MAGAGNIN LUCA (IT)
BESTETTI MASSIMILIANO (IT)
MAGAGNIN LUCA (IT)
| WO2003035923A1 | 2003-05-01 |
| DE10118763A1 | 2002-10-17 | |||
| DE19809932C1 | 1999-10-28 |
PATENT ABSTRACTS OF JAPAN vol. 018, no. 533 (C - 1259) 11 October 1994 (1994-10-11)
DATABASE WPI Section Ch Week 197847, Derwent World Patents Index; Class M11, AN 1978-84786A, XP002352823
PATENT ABSTRACTS OF JAPAN vol. 012, no. 373 (C - 534) 6 October 1988 (1988-10-06)
PATENT ABSTRACTS OF JAPAN vol. 015, no. 112 (C - 0815) 18 March 1991 (1991-03-18)
See also references of EP 1784523A1
The method is based on the use of light alloy coat¬
ing technologies (magnesium or aluminum) based on the
physical vapour deposition of titanium and the like (Ti,
Ta, Nb, Zr, Hf, W, V, Mo) and the subsequent colouring of
the metal (Ti, Ta, Nb, Zr, Hf, W, V, Mo) by electrochemi¬
cal oxidation.
A variation of the technique consists in the physi¬
cal vapour deposition of a layer of titanium or the like
(Ti, Ta, Nb, Zr, Hf, W, V, Mo) and the subsequent reac¬
tive physical deposition of a layer of TiO2 (or similar
oxide for the metals Ta, Nb, Zr, Hf, W, V, Mo) .
The most commonly used magnesium alloys are listed
in Table A below, together with the nominal composition.
Table A. Nominal composition (wt %) of magnesium alloys
The series of the aluminum alloys most commonly used is listed in Table B. Table B. Commonly used aluminum alloys.
In order to be coated by a thin layer R (in the or¬
der of micrometers) of titanium or the like (Ti, Ta, Nb,
Zr, Hf, W, V, Mo) , the surface of the base metal indi-
cated with LL in figures 3a, 3b, 4, (light magnesium or aluminum alloy) must be adequately prepared. The pretreatment PR of the surface does in fact play an important part for allowing the development of a pro¬ tective coating R on magnesium and its alloys, or on alu- minum and alloys. The most common pretreatment operations PR are me¬ chanical finishing, chemical cleaning and the deposition of a galvanic coating (typically zinc, copper and nickel) . The mechanical finishing and chemical cleaning are indispensable for bringing the surface of the product to the optimal degree of roughness and decontamination, allowing it to receive a coating without problems of ad¬ hesion between the end-product, the substrate LL, and coating R (figure 3a) . Furthermore, the use of an inter- mediate coating SB of a galvanic nature, which forms a barrier layer, (figure 3b) , can be recommended for having a greater guarantee of protection of the substrate made of light alloy. If, for example, the end-product made of a magnesium alloy were not sufficiently protected from the titanium film, during the subsequent electrochemical colouring op¬ eration COL in an aqueous environment, there would be the dissolution of the magnesium rather than the titanium colouring. This marks a great difference with respect to the case of massive titanium colouring (tantalum, niobium, and the like) , for which there are no problems of this type. It could therefore be necessary to insert further intermediate protective layers between the film of tita¬ nium or similar products (Ti, Ta, Nb, Zr, Hf, W, V, Mo) and the magnesium or aluminum alloy. The pretreatment phases of the surface of the end-product made of light alloy, before the deposition of thin layers of metallic titanium and other products (Ti, Ta, Nb, Zr, Hf, W, V, Mo) and their colouring, are therefore extremely impor¬ tant. Magnesium or aluminum alloys are metals which are difficult to cover with humid methods. The layer of oxide which covers them must be removed before the deposition. In all cases, the coatings must have a very low po¬ rosity and the deposition solutions must not react vio¬ lently with the light alloy forming the substrate. The quality of the coating depends on the quality of the preparation of the end-product made of magnesium or alu¬ minum alloy; pretreatment methods suitable for the type of base alloy are therefore necessary. Figure 4 represents the sequence of operations starting from the end-product made of light alloy LL; the pretreatment PJ?; the coating R by the physical vapour deposition of a metal selected from titanium, tantalum,
niobium, zirconium, vanadium, hafnium, molybdenum, rhe¬
nium, tungsten; and the colouring COL by oxidation ac¬
cording to the invention.
Table C below summarizes the function of the pre-
treatment operations which precede the galvanic deposi¬
tion whereas, with reference to figure 5, two pretreat-
ment procedures of light magnesium or aluminum alloys are
illustrated.
Table C. Pretreatment operations of the surface of the
end-product made of a light alloy (Mg or Al)
In the scheme of figure 5, it can be seen how the pretreatment PR is effected according to two plating pro¬ cedures with zinc Zn or with chemical nickel NiA. After a cleaning PR and pickling DEC common to the two methods in the case of the zincate process, the acti¬ vation ZnA is effected followed by zincing in an alkaline solution of zinc Zn and the deposition of a copper Cu layer and a subsequent further coating R' is effected, if necessary. In direct plating, on the contrary, the activation NiA is effected by means of fluorides followed by plating PL with chemical nickel (electroless) and a further coat¬ ing R' , if necessary. In the case of a generic end-product made of the mentioned materials, with reference to figures 6a and 6b, the metallization and colouring process can also be ap¬ plied with a method of the "web coating" type. A suitably pre-treated material (for example: yarns, plastic films for packaging, galvanized sheet iron for cars, etc..) can be coated in continuous: the tape 2 (or thread) is un¬ wound from the spool 1 following the direction of the ar¬ row F, coated with a metal layer of titanium, in a reac¬ tor PVD, by means of the ionic beam assisted deposition technique, and rewound on the reel as a bobbin 3. The tape 6 coated with a titanium film is subsequently passed to the colouring step, for example electro-chemically. Also in this case, the technique can be adopted for un¬ winding the bobbin 3 of metallized tape, sending it into the colouring tank 4 equipped with a cathode 5, making it to act as anode, and then rewinding it on a reel 7. Fi¬ nally the metallized and coloured tape (or yarn) is pos¬ sibly protected by a transparent protective layer. The metallization can be effected by means of air- air systems, in which the tape enters the metallization reactor through low-medium-high vacuum zones, is metal¬ lized, and then exits passing through high-medium and low vacuum zones, until it returns into the atmosphere. As an alternative, the operation can be effected by implementing the whole unwinding-winding system in the metallization reactor. The electro-chemical colouring can be effected by means of brush methods. A brush soaked with an electro¬ lytic solution is put in contact with the surface to be electrochemically oxidized. A metal push-rod is present on the brush, which is connected to the negative pole (cathode) of a generator, the metal film is put in con¬ tact with the positive pole (anode) . In this way, the an¬ odic oxidation region can be localized and the colouring is subsequently effected by anodic oxidation in the areas in which the brush is in contact with the metallized sur- face . It is extremely important for the deposited layer to be sufficiently thick and adherent to the substrate, in order to electrochemically oxidize the surface of the metal deposited with the PVD technique. Furthermore, the thickness of the film deposited plays an important role in the current distribution in the film during the anodic oxidation operation. It is extremely important for the current to suita- bly reach all the surface points in order to electro¬ chemically oxidize the metal surface with the PVD tech¬ nique. Appropriate contact systems must therefore be pre¬ pared for the objects to be coloured, or with a high num- ber of electric current points in contact with the metal film. Colouring can be also effected directly in the met¬ allization reactor, for example by introducing in the magnetron sputtering reactor, at the end of the deposi- tion of the metal layer, an oxygen/argon mixture so that oxygen reacts with the metal (titanium and similar) form¬ ing a layer of coloured oxide. The deposition of titanium (Ti, Ta, Nb, Zr, Hf, W, V, Mo and alloys thereof) in the form of a thin layer can be effected using several techniques. The deposition technique and the operative parame¬ ters greatly influence the structure of the metallic films produced (dimensions, form and crystallographic orientation of the grains, defects, porosity, residual stress in the coating, and similar) . The film structure, in turn, influences the chemical and physical properties of the film itself. The PVD deposition is the preferred technique for depositing metals such as titanium and similar (Ti, Ta, Nb, Zr, Hf, W, V, Mo and alloys thereof) . The main physical vapour phase deposition techniques are listed hereunder: vacuum evaporation, wherein the material emitted from a thermal vaporization source, reaches the sub- strate without collisions with the gas molecules in the area between the source and the substrate; sputtering (cathodic ablation) in which the source of the vaporized material is the surface of one or more targets (cathode) , which are subjected to physical ablation (sputtering) . arc deposition, wherein a high current and low volt¬ age electric arc is shot in a low pressure gas, to erode the solid cathode or to melt and evaporate the anode; - ionic deposition which uses the bombardment of the developing film on the part of atomic particles hav¬ ing sufficient energy, to modify and control the composition and property of the film. These processes normally operate at pressures lower than (or close to) 1 mTorr or, according to the I.S. lower or close to 7.5 pascal (Pa) as 1 Pa corresponds to about 7.5 mTorr. These pressures can be reached by means of a pumping system equipped with a diffusion or turbo-molecular pump and a preliminary pump. The conceptual scheme of a physical vapour deposi¬ tion process (PVD) is shown in figure 7. The atoms of the metal to be deposited are emitted EV from a liquid or solid source (target) T to form the gas Gl (due to the heating, as a result of collision with ions of inert gas, and similar) and with a transport mechanism TR, mediated by the gas G2 which is present at low pressure in the deposition reactor, CND are deposited on the substrate under the form of a film F. In general it can be said that the structure of the deposited layer is determined by the competition between the atomic mobility (which depends on the substrate tem¬ perature) and the arrival rate of the particles on the surface . The ratio between the substrate temperature and the melting temperature of the metal deposited, Ts/Tf, is an extremely important parameter. Another very important parameter is the gas pressure in the reactor. The problem of the porosity of the titanium (tanta¬ lum, niobium, etc..) metal coating is represented by the high melting point of the metal deposited. In a PVD proc¬ ess the metal is vaporized and re-condensed on the sub¬ strate. If the conditions are not suitable, the film structure formed is porous. A densification effect is observed in deposition processes wherein a beam of energy particles (ionic bom¬ bardment) hits the developing metal. The deposition temperatures must be lower than the stability temperatures of the substrate B or the barrier layer SB, if present. Good adhesion, uniformity and low porosity of the titanium coating or similar (Ti, Ta, Nb, Zr, Hf, W, V, Mo and alloys thereof) , must be obtained. In PVD processes, the high substrate temperature favours the formation of coatings having a compact structure. High temperatures of the substrate however are not practicable in the case of low-melting substrates. It has been observed that other technical expedients can be used in order to reduce the temperature of the substrate without lowering the quality of the deposit: for example, by electrically polarizing the substrate. Physical vapour deposition assisted by ionic bom¬ bardment (IBAD : ion beam assisted deposition) , allows good quality films to be obtained. During the deposition phase, the film is struck, continuously or periodically, by highly energetic atoms of inert gas and by reactive particles which modify the development and properties of the film. The technique allows the film adhesion and the cov¬ ering of the film on the substrate, to be improved; more¬ over, by controlling the ionic bombardment, it is possi¬ ble to operate on the film properties (density, morphol¬ ogy and residual stress) . With reference to figure 8, the light interference is due to the optical path difference between the lumi¬ nous rays reflected on the oxide surface A and those re¬ flected by the surface of the metal B. ' This phenomenon gives rise to interference colouring. The colour depends on the thickness of the oxide film. Metals such as titanium, niobium, tantalum and simi¬ lar, oxidize in the air at room temperature, but the ox¬ ide film which is formed is too thin to provide interfer¬ ence colours. The simplest thickening method of the oxide film consists of heating the metal in air. The colouring of the metal layer, vapour deposited, can be effected by means of thermal or galvanic oxida¬ tion. The colouring can also be obtained by reactive physical vapour deposition of the metal oxide. In this case, argon/oxygen mixtures are used in the deposition reactor. By controlling the emission rate of the metal, the ionization degree of the gas and the ratio of the partial oxygen and argon pressures, an oxide layer is obtained which creates interference colours. The colours which are formed by heating the metal in air, depend on the- time and temperature of the treatment-. Table 1 of figure 9 indicates a chromatic scale example obtained by thermal oxidation of titanium in air. The electrochemical colouring of titanium is a tech¬ nique which is effected at room temperature by dipping the piece to be oxidized in an electrolytic solution and connecting it to the positive pole of a current genera- tor. A metal is connected to the negative pole, which acts as cathode (titanium, stainless steel and similar) . The electric scheme is shown in figure 10 (anode: manufactured product coated with Ti and similar,- cathode: titanium, stainless steel and similar) . The electrolytic solution can contain sulphuric acid (5%) or phosphoric acid (15%) or ammonium sulphate (10%) . Other solutions are possible. There are numerous colour¬ ing techniques: by immersing the piece in an electrolytic cell, or by brush anodization. The oxidation active area can be delimited by shields, lacquers and the like so as to localize the formation of the coloured oxide. The different colours are formed by varying the cell voltage. This method is extremely accurate as the elec- trie parameters, voltage and current, are easily con¬ trolled. In this way wide colour ranges can be obtained as shown as an example in table 2 of figure 11. The electrochemical oxidation is generally effected by anodic polarization of the end-product covered by a cell voltage ranging from 5 to 300 volt, according to the desired colour. The surface pre-treatment of massive titanium end- products plays an important role in the electrochemical development of the coloured titanium oxide. Before the electrochemical oxidation, the surface of the metal (Ti, Ta, Nb, Zr, Hf, W, V, Mo and alloys thereof) must be suitably prepared. The preparation cycles of the metals which can be coloured by electrochemical oxidation are based on me- chanical finishing, cleaning and surface activation steps . For example, the acidic activation of titanium can be effected by immersion in 10% by weight solutions of nitric acid and 2.5% hydrofluoric acid, for various tens of seconds . Tantalum can be attached by very aggressive acidic solutions: for example concentrated acids at boil¬ ing point. Niobium can be attached in solutions of sul¬ phuric acid (20%) and hydrofluoric acid (10%) at a warm temperature. Other solutions can be used. In the case of thin films produced by vapour deposi¬ tion, the preparation can be extremely simplified. The deposition of thin films is in fact effected under condi¬ tions of low oxygen concentration and if the target is extremely pure, the surface of the metal film which is deposited is also extremely pure. This makes the removal of the surface oxides before the electrochemical colour¬ ing less complex. The deposition phase comprises the deposition of a layer of metal selected from titanium, tantalum, niobium, zirconium, vanadium, hafnium, molybdenum, rhenium, tung¬ sten and their alloys in thicknesses preferably ranging from 1 to 20 micrometers. A very important problem which makes the electro¬ chemical oxidation of titanium (or similar) films with respect to massive titanium lies in the fact that in the anodic oxidation of titanium films, a correct current distribution must be obtained on the whole surface of the film. This aspect is linked to problems of electric con¬ ductivity through a metallic film which can also have the thickness dl of a micrometer or even less . The difficulty can be overcome by using massive con¬ ductor substrates on which the film is deposited, or by using barrier layers which contain metallic films depos¬ ited with the PVD or also galvanic technique, capable of sustaining the current in the anodization phase. The me¬ tallic film, for example copper, beneath the titanium (or similar) film will act, together with the titanium film itself, as a conductor in the oxidation operation. When the substrate or base B is of the metallic type, a good adhesion of the metallic film to the metal¬ lic substrate is typically obtained using surface prepa¬ ration techniques (with wet or vacuum methods) capable of removing the surface contamination and any possible layer which negatively influences the adhesion, and subse- quently depositing a material which easily binds with the base material . High surface temperatures stimulate the diffusive phenomena and often allow a better adhesion. Metal-metal pairs non-mutually soluble should be avoided, a good adhesion however can be obtained with non-mutually soluble metallic systems if the nucleation density during the PVD development is high. In order to obtain a good adhesion of the film de¬ posited with the PVD technique on metallic substrates, use is made of the continuous variation in the properties of the interfacial region, by controlling the PVD deposi¬ tion parameters. The barrier layer must also act as an adhesion promoter, in the sense of attenuating all states of interfacial stress between the substrate and the film deposited. These states of interfacial stress can cause delamination and are due, for example, to different dila¬ tion coefficients of the materials or to differences in the crystalline or morphological structure. For this rea¬ son, nickel is often a good material as it binds with many metals and is ductile. In many cases, the metal oxide is removed during the outer cleaning process and the small quantities reformed after the cleaning are removed by activation in situ in the deposition reactor. If the natural oxides on the sur¬ face are not removed, then the metal deposited should have a high affinity for oxygen. With respect to the application field relating to the metallic materials of the present application, dis¬ tinction should be made between ferrous and non-ferrous metallic materials. Ferrous metallic materials for the application of the present invention are: steels, cast irons, inox steels . Non-ferrous metallic materials for the application of the present invention are: copper and copper alloys, nickel and nickel alloys, cobalt and cobalt alloys, zinc and zinc alloys. The surface of the metallic materials used as sub¬ strate must be pretreated before the application of the barrier layer and metallization layer or the direct ap- plication of the metallization layer. The pretreatment operations depend on the type of metallic material used. It can generally be said that the pretreatment op¬ erations can be of the mechanical type or chemical or electrochemical type. Among important operations of the mechanical type, sandblasting and mass finishing can be mentioned in par¬ ticular. Among important operations of the chemical or elec¬ trochemical type, cleaning with organic or aqueous sol- vents, acid or alkaline surface activation, the chemical deposition of metallic layers (copper and nickel) , the galvanic deposition of metallic layers or electro- finishing, can be mentioned. Polymeric materials offer numerous possibilities from a metallization and colouring point of view. The chemical properties of a polymeric surface de¬ pend on the functional groups present on the surface. The mechanical properties of the surface region de¬ pend on the quantity and type of bonds which are formed there and are generally different from those of the mate¬ rial body. In order to obtain a good adhesion, the surface of the polymer must be free of contaminants . The adhesion of a metallic film to a polymeric sur- face can be obtained using metals which form organometal- lic bonds with the substrate. Among the main metals, Al, Cr, Ti (Ta, Nb, etc) can be mentioned. The surface of the polymer can be pretreated in plasma to make the surfaces more reactive with an increase in the nucleation density and of the bonds . Oxygen or nitrogen plasmas are generally used to ac¬ tivate the surfaces. Also in this operation, care should be taken not to overexpose the surfaces to the plasmas, with the conse- quent formation of weakened interfacial regions and therefore with a reduced adhesion. Improved adhesion can be obtained by roughening the surface and having a mechanical hooking between the film deposited and the surface. Plastic materials which are industrially subjected to vacuum metallization are: acrylics, acrylonitrile- butadiene-styrene (ABS) , polyamide (PA) , polybuty- leneterephthalate (PBT) , polycarbonate (PC) , polyester, polyethersulfone (PES) , polyethylene (PE) , polyethyl- eneterephthalate (PET) , polyphenyleneoxide (PPO) , poly¬ propylene (PP) , polysulfone, polyvinylchloride (PVC) . Plastic materials require an adequate pretreatment before metallization. The primary purpose is to remove the contaminants which can cause poor adhesion, a low- quality finishing, etc. The cleaning is effected by means of organic or wa¬ ter-based solvents. An example of a metallization process with titanium or the like, of plastic materials consists in the appli- cation of three layers: - A base layer, this is an organic coating, also called base-coat, whose main function is to produce a smooth surface so that the metal deposited is shiny; it is also used for improving adhesion between the metallic coating and the substrate. The base layer also acts as a seal of the substrate surface for the gases which are released from the plastic material during the vacuum set-up of the deposition reactor. Many plastic materials can be metal¬ lized directly but the results are generally unsatisfac- tory, except for acrylic materials and polycarbonates. In the case of thin films, all surface edges and faults are faithfully reproduced. For this reason, the surfaces are generally prepared by the application of an organic base layer (SB) . This layers allows a satisfactory adhesion, it fills small defects or holes in the surface of the substrate and provides a smooth surface for the metalli¬ zation. - A metallization layer deposited with vacuum techniques (PVD) . This is the titanium layer (or similar and their alloys) . - A coating layer applied on the metallic oxide which produces interference colours,- this layers is also called top-coat and its main function is to protect the metal and metal oxide. In some cases, the top-coat is not ap- plied. The top-coat can be deposited directly in the re¬ actor (quartz layer deposited with the PECVD technique) . The top-coat can be an organic material which hardens due to UV or thermal action. One of the main factors which cause the durability of a coating is adhesion to the substrate. Metals which form strong stable chemical bonds with the substrate firmly adhere, whereas metals which only form physical bonds can become more easily detached from the substrate. The maximum thermal treatment temperatures of the organic layers, used as barrier layer (SB) and protective layer (RIV) of the metallization, should be selected in relation to the type of plastic material. As an indica¬ tive example: polystyrene 60-650C; acrylic 65-800C; ABS 80-900C; phenol and urea 110-1500C; polycarbonate, poly- propylene and polysulfone 130-1500C. The type of plastic material to be metallized is the determinant factor in selecting the composition of the organic layers. There are numerous specific commercial organic formulations for the various types of plastics and for the protection of the metallization layer. Exam¬ ples of formulations for organic layers can be the fol¬ lowing: a) base layer: 1) nitrocellulose resin modified in a solvent (sys- tern of ketones, alcohols, glycol ether and aromatic hy¬ drocarbons) which easily evaporate in air; 2) alkyd resin amino-modified in solvents based on aromatic hydrocarbons, alcohols and esters; 3) alkyd resins modified in aromatic and aliphatic hydrocarbons, or glycol ether,- 4) epoxy-acrylate resins, unsaturated acrylate, ac- rylate esters in a solvent based on methylisobutylketone and isopropyl alcohol, with photo-setting agents which, when exposed to UV radiation, begin the setting process; b) protective layer: Epoxy modified acrylic resin in n-butanol and xylol, sometimes with the addition of 2-ethoxyethanol . The formulations for the base layer can have a non¬ volatile content ranging from 30% to 50% by weight, whereas the formulations for the protective layer can have a non-volatile content ranging from 20% to 30% by weight . The application of the organic layers can be ef¬ fected automatically or manually by: a) immersion; b) flow or shower; c) spraying. The setting of the organic layers is extremely im¬ portant, it must in fact be complete, especially in the case of the base layer. In the contrary case, there is the release of gases during the vacuum deposition. The volatile substances en¬ trapped in the organic product can migrate during evapo¬ ration allowing penetration of the metal and creating iridescence phenomena. The production of plastic components requires a good surface preparation. It is preferable to clean the plastic surfaces up¬ stream of the coating treatment with organic film, using, for example, water-based or organic-based solvents. If the organic solvent can have a good capacity of eliminat- ing the organic contaminants, it can, on the other hand, damage the plastic material on which the metallic layer is to be deposited. Environmental problems relating to the release of solvents into the atmosphere should also be taken into consideration. The cleaning can be effected in solvent vapours, by- immersion in liquid phase - or a combination of both. The stirring of the plastic components in ultrasounds can help to remove the contamination from recesses, blind holes, etc. When the plastic components are not coated by an or¬ ganic layer, the cleaning can be effected in the vacuum deposition chamber, by adding a plasma assisted activa¬ tion station and subsequently eliminating the cleaning as a separate process step. In this way, excellent adhesion of the metallic film to the plastic can be obtained. The vacuum metallization of plastic materials offers many openings for engineering and design, as it can be used for the substitution of components previously made with other materials. The plastics to be metallized must have a uniform composition and should not release vola¬ tile substances under vacuum. As plastic materials are good insulators, they have the disadvantage of becoming electrostatically charged, attracting dust. This necessi¬ tates cleaning and preparation treatment. Non-removed volatile substances can contaminate the metallization system and ruin the work. Furthermore, plastics (unlike glass and metals) desorb gases with va¬ pours extremely slowly. In many cases the metallization plants are generously equipped with adequately powerful vacuum systems. Examples of pretreatment of plastic materials before metallization are based on chemical activation in tetra- chloromethylene, or in concentrated sulphuric acid and subsequent washing in water. A further example is represented by activation with oxygen or ionic bombardment treatment . One of the most common types of pretreatment consist in surface roughening by means of sandblasting. The mi¬ cropores act as nucleation and anchoring sites of the me- tallic film. These types of pretreatment are important in the case of multiphase polymers in which one of the phases is preferably attacked. By attacking ABS, styrene-butadiene polymer, for example, the butadiene component is prefera- bly attacked and solubilized. Problems can arise in at¬ tacking materials reinforced with fibres as they require long activation times of the fibre with the risk of de¬ grading the matrix of the material . One of the problems of chemical pretreatment is that the use of additives, which increase the thermal and me- chanical resistance of the polymer, requires more aggres¬ sive chemical agents, and this can be a limitation. Other techniques frequently used for improving adhe¬ sion are treatment with flames (flaming) , crown dis- charge, activation in oxygen plasma. For these types of pretreatment, the surface modification mechanism is the formation of a wide range of functional groups containing oxygen. These modifications, however, change the surface of the polymer. The plastic material ABS, for example, is treated with an oxygen plasma before the metallization application. The surfaces can be treated in the plasma of inert gases. The activation in this case is probably "due" to" the UV radiation from the plasma. The treatment of polymers in plasma can cause tex¬ tures and improves the adhesion strength with a mechani¬ cal interlocking mechanism. The texture can be accompa¬ nied by a variation in the chemistry of the surface due to the variation in the terminal species. For depositing an aluminum film on Kapton, for exam¬ ple, an optimum surface treatment for Kapton has proved to be a detergent washing followed by caustic attack to roughen the surface and subsequently UV treatment under partial oxygen pressure which oxidizes the surface. The activation of the polymeric surfaces can be ef- fected by the deposition of an additional polymer layer which is more subject to the formation of bonds. Mechanical brushing of the surface is a technique which destroys the oxide and exposes the metal producing an improved adhesion of the coatings deposited under vac¬ uum on a steel tape. The sensitisation consists in the addition of small particles of material on the surface which act as nuclea- tion sites. Ionic implanting can also be used for introducing foreign elements into the material and improving adhe¬ sion. The pre- and post-me'tallization varnishes can be of the traditional type: with solvent, water, hardenable with UV rays. The premetallization varnishes can be applied for example to polymeric materials (PP, Nylon, ABS, etc.) , metals, glass, etc. Mixed water and solvent treatment cycles can be used. The UV hardening varnishes require short hardening times . Wood, leather and natural fibres of an animal or vegetable origin and cellulose materials can be protected and decorated with the application by means of PVD tech- niques of one or more metallic layers and an oxide layer which creates interference colours. Among the most common types of wood, the following can be cited: soft wood (fir, pinewood, sequoia, etc.) , hard wood (birch, cherry, beech, nut, oak, etc.) and ex¬ otic hard wood (ebony, mahogany, teak, etc.) . The metallization of these materials should take into account the fact that they degas under vacuum. The metallization can be preceded by the application of a base layer, for example of a photo-polymerizable fil- mogenic material with UV radiation, suitable for sealing the material to prevent the release of gas and to promote the uniformity and" adhesion of the metallic coating. The sealing phase of the pores with a base layer which can consist, for example but not exclusively, of a thermosetting polymeric material, UV setting, or metallic material (for example nickel deposited with a wet auto- catalytic method), is extremely important. A layer of titanium is then deposited with PVD proc- esses on the metallized wood material. The metallization treatment and colouring can be ap¬ plied to glass and ceramic. On the basis of their composition and utilization, the following types of glass can be distinguished: silica glass, 96% silica (Vycor™) , sodium-calcium glass, lead silicate, high lead silicate, borosilicate, aluminum- boro-silicate, aluminumsilicate . Upon heating some types of glass in air, the mobile species (sodium) segregate on the surface and form nod- ules which, if not removed in the pretreatment phase, cause dotting in the metallization film. "Float" glass is the type which is most commonly metallized with the PVD technique. The side of the glass which has been in contact with the molten tin can be con- taminated by a tin oxide. In the pretreatment phase, the tin oxide can be removed with a light attack with a solu¬ tion of ammonium bifluoride. A further cause of the surface contamination of glass is represented by the packaging and storage phases. In some cases, the adhesion of the metallic film to the surface of glass increases with time after the depo¬ sition, as reactions in the solid state take place at the interface, which can proceed very slowly after deposi¬ tion. This can be due to the diffusion of reactive spe- cies such as oxygen at the interface or by the release of the film stress with time. The cleaning with plasma of a glass surface before deposition of the metallic film has proved, for example, to improve the adhesion of the film with time. Metals having a strong affinity for oxygen generally form well-adhering coatings on glass. It is known that in the first moments after the deposition of titanium on py- rex glass, a layer of TiO is formed, which facilitates adhesion. Adhesion to the surface of glass is generally ob¬ tained by preparing a decontaminated surface and using a material having a high affinity for oxygen, such as for example, Ti and similar products. Furthermore, in order to reduce internal stress of the film, the thickness of the titanium film should be limited and the desired prop¬ erties generated using a multilayer structure. If the first atomic interfacial layers do not have an affinity -for oxygen, a su-r-face chemist-r-y or- conductive deposition can be used which forms a high density of nu- clei . In some cases, the nucleation density can be in¬ creased by initiating the deposition with oxygen, resid¬ ual in the environment or adsorbed on the surface of the substrate, which has a strong affinity with the film of material which is deposited. In some cases, a high initial deposition rate in¬ creases the nucleation density on the surface. The sur¬ face chemistry of the oxides can be altered with selec¬ tive treatment which modifies the composition and nuclea¬ tion of the ad-atoms on the surface. In the deposition of a film of compounds on oxides, good adhesion can be obtained by generating an interface with a composition gradient and being certain that a minimum residual stress is exerted. Ceramic materials can also be subjected to metalii- zation and colouring. Traditional ceramic materials are classified as follows: traditional ceramics, brickwork, tiles, sanitary products, technical porcelains, refrac¬ tory materials. Ceramics for traditional use can be subdivided ac- cording to their structure into porous or greified, de¬ pending on the surface state into glazed or unglazed, and in relation to the colour into white or coloured. In the ' colouring of massive metals by~ oxidation," thermal or galvanic, the thin layer of oxide is produced by the reaction of the metal with oxygen, according to the reactions: Ti + O2 (g) = TiO2 thermal Ti + 2H2O = TiO2 + 4H+ + 4e~ electrochemical In the case of titanium, for example, with an in- crease in the time and treatment temperature of the ox¬ ide, there is a colour variation along chromatic scales. End-products made of magnesium or aluminum alloys do not tolerate high temperatures and consequently the ther¬ mal oxidation of the titanium (or similar) film which covers the light alloy end-product must be carried out at sufficiently low temperatures for longer times, depending on the type of light alloy used. Vice versa, the electrochemical colouring of tita¬ nium is a technique which is effected at room temperature by immersing the piece to be oxidized into an electro¬ lytic solution and connecting it to the positive pole of a current generator. A metal which acts as cathode (titanium, stainless steel, etc.) is connected to the negative pole. The electric scheme is shown in figure 7 (anode: light alloy coated with Ti and similar products; cathode: titanium, stainless steel, and the like) . The electrolytic solution can contain sulphuric" acid (5%) or phosphoric acid (15%) or also ammonium sulfate (10%) . Other solutions are possible. There are a numerous colouring techniques: by immersion of the piece in an electrolytic cell, or by brush anodization. The active oxidation area can be delimited by shields, lacquers, and the like so as to localize the formation of coloured ox- ide. The various colours are formed by varying the cell voltage. This method is extremely accurate as the elec¬ tric parameters, voltage and current can be easily con¬ trolled. In this way wide colour ranges can be obtained. Electrochemical oxidation is generally effected by anodically polarizing the coated end-product at a cell voltage ranging from 5 to 300 volts, in relation to the desired colour. The preparation of the titanium surface plays an itn- portant role. The mechanical resistance of anodic films made of titanium and similar metals (Ti, Ta, Nb, Zr, Hf, W, V, Mo) is greatly conditioned by the state of the sur¬ face downstream of the physical vapour deposition. Before the electrochemical oxidation, the surface of the metal (Ti, Ta, Nb, Zr, Hf, W, V, Mo) must be suitably prepared. The preparation cycles of metals which can be col¬ oured by means of electrochemical oxrdation are base'd on mechanical finishing, cleaning and acid activation stages. The acid activation of titanium, for example, can be effected by immersion in solutions of nitric acid 10% by weight and hydrofluoric acid 2.5%, for tens of sec¬ onds. Tantalum can be attacked with very aggressive acid solutions: for example, acids concentrated at boiling point. Niobium can be attacked in solutions of sulphuric acid (20%) and hydrofluoric acid (10%) at a warm tempera¬ ture. Other solutions can be used. In the case of thin films produced by vapour phase deposition, the preparation can be extremely simplified. The deposition of thin films, in fact, takes place under conditions of low oxygen concentration, and if the target is very pure, the surface of the metal film which is de¬ posited is just as pure. This makes the removal of the surface oxides before the electrochemical colouring less complex. The deposition phase comprises the deposition of a metal layer selected from titanium, tantalum, niobium, zirconium, vanadium, hafnium, molybdenum, rhenium, tung¬ sten in thicknesses preferably ranging from 0.5 to 50 mi- crometers, and even more preferably ranging from 1 mi¬ crometer to 10 micrometers. Deposition and colouring tests The experimental tests were carried out using sam¬ ples made of magnesium alloy AM60B. Metal plates (10 cm x 10 cm x 0.5 cm) , were cut from ingots of magnesium alloy AM60B, using a belt saw. The surface finishing was im¬ proved, by smoothing the surface of the samples with sandpaper (up to 1200 grits) . The samples were washed in acetone, abundantly rinsed with distilled water, pickled in diluted nitric acid, rinsed again in distilled water. At this point, the samples were subjected to coating treatment with titanium by means of the physical vapour deposition technique. The deposition reactor is of the sputtering magne- tron type and is equipped with an ionic source. The ionic source was used to clean and activate the surface of the sample before deposition, effected with the sputtering magnetron technique. Both the activation and cleaning phase with the ionic source and the sputtering magnetron deposition phase were carried out in an argon atmosphere at a low pressure (in the order of mTorr) . The electrochemical colouring was effected by ano¬ dizing the titanium film having a thickness of a few mi¬ crometers and deposited on magnesium alloy. An electro¬ lyte based on sulphuric acid (at 5%) was used, exerting cell voltages in the order of tens of volts. Test 1 (Mg) Ionic source
The magnesium alloy substrate was uniformly coated on the whole surface . The thickness of the coating is a few microns. There are no signs of delamination of the coating. The porosity is extremely low: upon placing a drop of acid on the titanium surface, no hydrogen development due to the attack of the magnesium, was observed, even after prolonged exposure. If the titanium film were porous, a strong hydrogen development due to the dissolution reaction of the under- lying magnesium, would in fact be observed. The colouring of the titanium film on magnesium al¬ loy was effected electrochemically. The sample of magnesium" alloy AM60B" coating with; ti"- tanium (5-10 micrometers) was anodically polarized in sulphuric acid at 5% against a massive titanium elec¬ trode, at a cell voltage of a few tens of volts. After a few seconds, the titanium was coated with a bluish-purple-coloured oxide. Test 2 (Mg) Ionic source
Magnetron sputtering
The coating is compact and uniform. It does not de- laminate from the substrate and with the drop of sul¬ phuric acid test, it proves to be non-porous. Under slightly different voltage conditions with re¬ spect to Test 1, the colouring obtained is a uniform blue colour on the surface. Test 3- (Al-) A coating and colouring test of a sample made of aluminum alloy 6060 was effected. The aluminum sample (10 cm x 5 cm x 0.2 cm) was smoothed with paper (up to 1200 grits) , was washed in acetone and subsequently with de- ionized water. This pretreatment phase was followed by the ionic cleaning phase in the deposition reactor. A ti¬ tanium layer was then deposited. Ionic source Magnetron sputtering
The coating is compact and uniform. A tear test was effected with adhesive tape. There were no delaminations of the titanium film from the substrate. The aluminum alloy sample coated with titanium was electrochemically coloured with a light blue colour, un¬ der identical voltage conditions to those of test 2. Some examples of ""the coTouring of end-products are- provided below. Example 1 A flat UNS 316 stainless steel sample was subjected to titanium coating followed by electrochemical colour¬ ing. The surface of the sample was degreased with isopro- pylic alcohol. The deposition cycle of the titanium layer envisaged an initial activation phase with the use of an ionic source: the activation treatment lasted 5 minutes at 1.9 mTorr of argon pressure at a voltage of 1.4 kV. This was followed by a coating phase using the physical deposition technique of the magnetron sputtering type: the coating treatment lasted 20 minutes at 1.9 mTorr of argon pressure; the sputtering current was 6.6 A. The re¬ sult was a deposit in the order of a micrometer with a dark grey shiny appearance. There was an extremely good adhesion of the titanium to the stainless steel. The ti- tanium layer was coloured by anodic oxidation in a solu¬ tion of phosphoric acid, at a voltage of 20 V, obtaining a violet-blue-coloured layer of titanium oxide. This was followed by the varnishing phase with a layer of trans¬ parent varnish with protective water for metals. Example 2 A flat CZ 121 M brass sample was subjected to coat¬ ing with a barrier layer of the metallic type followed by titanium coating and finally electrochemical colour¬ ing. The surface of the brass sample was degreased with acetone and deoxidized by immersion for 5 minutes in a sulphuric acid solution (20% by weight) at room tempera¬ ture. The brass substrate was activated with a commercial solution of Sn/Pd by immersion at room temperature for 2 minutes. This was followed by metallization by the auto- catalytic deposition of Ni-P alloy in a bath having the following composition and characteristics: nickel acetate 0.12 M, sodium hypophosphite 0.32 M, lactic acid 0.5 M, pH 4.7, operating temperature 85°C. The deposition of nickel-phosphorous was carried out for 30 minutes produc- ing a deposit having a thickness of 10 μm. The deposition cycle of the titanium layer was based on an initial acti¬ vation phase with the use of an ionic source: the activa¬ tion treatment lasted 5 minutes at 1.9 mTorr of argon pressure at a voltage of 1.4 kV. This was followed by the coating phase by means of the magnetron sputtering tech¬ nique: the coating treatment lasted 20 minutes at 1.9 mTorr of argon pressure; the sputtering current was 6.6 A. A deposit was formed in the order of a micrometer with a dark grey shiny appearance. There was an extremely good adhesion of the titanium to the stainless steel. The ti¬ tanium layer was coloured by anodic oxidation in a solu¬ tion of phosphoric acid, at a voltage of 20 V, obtaining a vrolet-blue-coloured" layer of ■titan±um~oxrde " Example 3 A sample made of copper-tin alloy (white bronze) was coated with a layer of tantalum by means of the magnetron sputtering technique. The layer was deposited after cleaning the surface of the sample with acetone and acti¬ vation in sulfamic acid. The tantalum deposition was ef- fected for a period of 10 minutes at an argon pressure of 1.9 mTorr and a sputtering current of 6.4 A. The deposit was electrochemically coloured in a solution of sulfuric acid. Example 4 A product made of ABS plastic material was subjected to coating with zirconium and subsequently electrochemi¬ cal colouring. The metallization was effected with the magnetron sputtering technique: 15 minutes at 1.9 mTorr of argon pressure, a sputtering current of 6.6 A. A thin deposit was formed which was subjected to electrochemical colouring by means of anodic oxidation in a solution of phosphoric acid. The result was an object made of ABS plastic coated with a coloured layer of zirconium oxide. Example 5 A product made of ABS plastic material premetallized with a copper layer, was subjected to coating with tita¬ nium and subsequently electrochemical colouring. The ti¬ tanium deposition -was- effected with the magnetron--sput¬ tering technique: 15 minutes at 1.9 mTorr of argon pres- sure, a sputtering current of 6.6 A. A thin deposit was formed (less than a micrometer) which was subjected to electrochemical colouring by means of anodic oxidation in a solution of phosphoric acid. The result was an object made of ABS plastic coated with a coloured layer of tita- nium oxide. The metallic copper barrier layer acted as an adhesion layer for the titanium and also as a current- carrier in the electrochemical colouring phase. Example 6 A product made of ABS plastic material was subjected to coating with titanium with the magnetron sputtering technique and then colouring with the reactive magnetron sputtering technique. The surface of the ABS plastic ob¬ ject was subjected first to the deposition cycle, with activation in oxygen plasma (2.20 mTorr) for 5 minutes. The metallization was effected with the magnetron sputtering deposition technique: 2 minutes at 1.6 mTorr of argon pressure. At 6.6-6.7 A of sputtering current. The colouring of the ABS plastic object was effected with the reactive magnetron sputtering technique: the deposition was effected for 3 minutes and 30 seconds at 6.6-6.9 A of sputtering current using an argon-oxygen mixture whose total pressure was 2.5-2.7 mTorr. The "result" was an ABS*~~p"lastic object coated" with a~ yellow-coloured layer of titanium oxide. Example 7 Several sheets of boron silicate glass (4 cm x 5 cm x 0.5 cm) were subjected to metallization by coating with titanium and subsequent electrochemical colouring. The titanium deposition was effected using a reactor of the magnetron sputtering type. The glass sheets were degreased in acetone. The •deposition cycle envisaged an initial activation phase using an ionic source: the activation treatment lasted a few minutes at 2.0 mTorr (argon) at a voltage of 1.3 kV. A coating phase followed, by means of magnetron sputter- ing: the coating treatment lasted 20 minutes at 1.9 mTorr (argon) ; the sputtering current was 6.6 A. The result was a deposit in the order of a micrometer with a dark grey shine appearance. The glass sheets coated with the tita- nium layer were coloured by anodic oxidation in a solu¬ tion of phosphoric acid. Glass sheets were produced with varying colours depending on the cell voltage applied. Example 8 A quartz glass ball was metallized and coloured with the technique described above. The metallization was car¬ ried out with the magnetron sputtering technique preceded by ionic activation with argon. The colouring was ef¬ fected" electrochemically in a solution of~ sulfuric ~acid7 A bulb was produced with a blue-coloured outer layer. Example 9 A ceramic tile (glazed stoneware) , having dimensions of 10 cm x 10 cm x 1 cm, was subjected to a coating cycle with titanium and subsequent electrochemical colouring. The titanium deposition was effected using a reactor of the magnetron sputtering type. The surface of the tile was degreased with acetone. The deposition cycle envisaged an initial activation phase using an ionic source: the activation treatment lasted 5 minutes at 1.9 mTorr of argon pressure at a voltage of 1.4 kV. A coating phase followed, by means of magnetron sputtering: the coating treatment lasted 20 minutes at 1.9 mTorr of argon pressure; the sputtering current was 6.6 A. The result was a deposit in the order of a few micrometers with a dark grey shine appearance. The titanium adhesion was extremely good. The ceramic tile coated with the thin layer of titanium was subjected to an electrochemical colouring test, by means of anodic oxidation in a solution of phosphoric acid. The result was a ceramic tile metallized with a blue-coloured layer of titanium oxide. Example 10 A ceramic tile (glazed stoneware) , having dimen¬ sions- of 10 "-cm- x 10 cm- x 1 cm, was -subjected-to a coating cycle with titanium with the evaporation technique and subsequent electrochemical colouring. The evaporation was carried out under a vacuum of 0.1-10 mPa. A titanium layer of about 1.5 micrometers was deposited. The titanium layer was electrochemically coloured, with a similar technique to that described in the previ¬ ous examples. Example 11 A ceramic tile (glazed stoneware) , having dimensions of 10 cm x 10 cm x 1 cm, was subjected to a coating cycle with titanium with the cathodic arc technique and subse- quent electrochemical colouring. The evaporation was carried out under a vacuum of 0.001-0.1 Pa. A titanium layer of about 2 micrometers was deposited, which was well adhered to the substrate. The titanium layer was electrochemically coloured, with a similar technique to that described in the previ¬ ous examples . Example 12 A ceramic tile (glazed stoneware) , having dimensions of 10 cm x 10 cm x 1 cm, was subjected to a coating cycle with titanium with the magnetron sputtering technique and subsequent electrochemical colouring. The~surface Of~the tile" was "degreased with" acetone". The deposition cycle envisaged an initial activation phase using an ionic source: the activation treatment lasted 5 minutes at 1.9 mTorr of argon pressure at a voltage of 1.4 kV. A coating phase followed, by means of magnetron sputtering: the coating treatment lasted 20 minutes at 1.9 mTorr of argon pressure; the sputtering current was 6.6 A. The result was a deposit in the order of a few micrometers with a dark grey shine appearance. The adhesion of the titanium to the tile was extremely good. The ceramic tile coated with the thin layer of ti¬ tanium was subjected to an electrochemical colouring test, by means of anodic oxidation in a solution of phos- phoric acid. It was possible to obtain a multicoloured surface by acting on the cell voltage during the anodic oxidation. Example 13 A ceramic tile (glazed stoneware) , having dimensions of 10 cm x 10 cm x 1 cm, was subjected to a coating cycle with titanium with the magnetron sputtering technique and subsequent electrochemical colouring. The surface of the tile was degreased with acetone. The deposition cycle envisaged an initial activation phase using an ionic source: the activation treatment lasted 5 minutes at 1.9 mTorr of argon pressure at a voltage'"Of" l".4"~kV~. A coating phase followed", "~by~ means~of magnetron sputtering: the coating treatment lasted 1 min- ute at 1.7 mTorr of argon pressure; the sputtering cur¬ rent was 6.6 A. At the end of the deposition, the deposi¬ tion of titanium oxide was effected with the reactive magnetron sputtering technique by introducing an argon- oxygen mixture (total pressure of 2.6 mTorr) for a time of 3 minutes at 6.7-6.8 A. At the end of the test a col¬ oured surface of titanium oxide was produced. Example 14 A sample of beech-wood was sealed with a thermoset¬ ting organic layer. It was then metallized by thermal evaporation. A metallic titanium layer was formed, having a thickness of 1 micrometer. The titanium layer was elec- trochemically coloured. Example 15 A 5 cm x 5 cm sample of cotton fabric was subjected to titanium deposition by means of vacuum evaporation. The thermal evaporation was effected in a reactor at a pressure of 0.1-10 mPa for a few minutes. The titanate fabric was subjected to electrochemical colouring. Example 16 A 20 cm x 20 cm sample of cotton fabric was sub¬ jected to the deposition of titanium by means of magne¬ tron sputtering and titanium oxide by means of reactive magnetron sputtering. The titanium- deposition-- was —ef¬ fected in an argon atmosphere (1.7 mTorr) for 30 seconds. At the end of the titanium deposition, an argon/oxygen mixture was introduced into the reactor, regulating the total pressure at a value of 2.13 to 2.7 mTorr for a pe¬ riod of 4 minutes. A sample of cotton fabric was pro¬ duced, coloured (purple-brown) on the side exposed to the target. Example 17 A polyethylene sheet was subjected to metallization with titanium using the thermal evaporation technique. The thermal evaporation was effected in a reactor at a pressure of 0.1-10 mPa for a few minutes. The titanate fabric was subjected to electrochemical colouring. Example 18 The metallization and colouring of various glass containers (perfume bottles) . The glass bottles were cleaned in acetone and in isopropylic alcohol. They were placed inside the deposition reactor under vacuum. The magnetron sputtering deposition was preceded by an acti¬ vation phase with argon plasma (1.85 mTorr at 1.6 kV and 0.3 A) which lasted 5 minutes. The titanium deposition via magnetron sputtering lasted 20 minutes at 1.70-1.80 mTorr of argon pressure, at a sputtering current of 6.6-6.9 A and a voltage of 365-~385-~V. At the end~ of the deposition the- bottles-were uniformly coated by a titanium layer. The titanium layer is compact, shiny and adherent. There are no signs of de¬ tachment . The bottles coated with a titanium film were sub¬ jected to electrochemical colouring in a solution of phosphoric acid. Bottles were obtained, having a uniform blue colour and a uniform blue-cobalt colour. Example 19 A pyramid-shaped glass bottle (used for food) was metallized adopting the deposition parameters of the pre¬ vious test. The metallization with titanium was effected via magnetron sputtering with a correct result. The tita- nium layer is uniform and adherent on the whole layer. The electrochemical colouring was effected in a solution of phosphoric acid at room temperature and produced a uniform dark-yellow-coloured titanium oxide. Example 20 A glass container (such as a sugar bowl) was sub¬ jected to metallization with titanium by means of the magnetron sputtering technique and colouring by the depo¬ sition of titanium oxide using the reactive magnetron sputtering technique. The basic vacuum in the deposition reactor was 3 x 10"3 Pa. The titanium deposition was pre¬ ceded by an ionic activation phase (Kauffman-type source) in argon plasma at 1.80 mTorr of pressure for 5 minutes at 1.4 kV and 0.22 A. The titanium deposition via magnetron sputtering lasted 4 minutes, at 6.7-6.8 A, with pressure values of 1.69-1.93 mTorr of argon. At the end of the deposition, the deposition of titanium oxide was effected with the reactive magnetron sputtering technique introducing an argon-oxygen mixture (total pressure of 2.50-2,80 mTorr) for a time of 4 minutes at 6.7-6.9 A. At the end of the test, a glass container was produced, uniformly coated by a layer of titanium and coloured titanium oxide with typical interference colours. Example 21 A C70 carbon steel sheet with a thin perlite struc¬ ture was metallized and coloured using the parameters of the previous test. The dimension of the sheet was 15 cm x 20 cm with a thickness of 0.5 mm. The titanium deposition was effected in a magnetron sputtering reactor, starting from a basic pressure of 2.5-10"3 Pa. The sample was subjected to ionic activation in argon at 1.76 mTorr, 16 kV and 0.26 A for a period of 5 minutes. The steel sheet was then coated with a layer of ti¬ tanium by means of the magnetron sputtering technique, at an argon pressure of 1.5-1.7 mTorr and a sputtering cur¬ rent of 6.8 A and a voltage of 375 V. The sheet coated with titanium was then coated with titanium oxide by means of the reactive magnetron sput¬ tering technique, using an argon-oxygen mixture at a pressure of 2.2-2.5 mTorr, for 4 minutes at 6.5-6.8 A. A steel sheet was produced coated by a layer of ti- tanium and a layer of titanium oxide with the typical colours of light interference phenomena. A transparent organic layer was applied to the col¬ oured sheet. The organic layer was applied with a brush. A drying phase followed for a few minutes at room tem- perature. Example 22 A glass bottle (of the type used for food) was sub¬ jected to metallization with titanium (magnetron sputter¬ ing) and colouring with titanium oxide (reactive magne- tron sputtering) . The bottle was cleaned in acetone and isopropylic alcohol. The bottle was then placed in the deposition and ionic activation reactor. The ionic activation (Kauffman source) took place with an argon pressure of 1.84 mTorr and a voltage of 1.4 kV and 0.22 A. The titanium deposition (magnetron sputtering DC) was effected" for 3 minutes at 1.-7-1.8 mTorr - of argon pressure at 6.8 A of sputtering current . The deposition of titanium oxide (reactive magnetron sputtering DC) was effected for 6 minutes in an argon- oxygen mixture at a total pressure of 2.4-2.6 mTorr and 6.8 of sputtering current . The result was a bottle coloured with light inter- ference colours. Example 23 A cardboard sheet (of the type used for food) was subjected to metallization with titanium (magnetron sput¬ tering) and colouring with titanium oxide (reactive mag- netron sputtering) . The titanium deposition (magnetron sputtering DC) was effected for 1 minute at 1.6 mTorr of argon pressure at 6.7 A of sputtering current. The deposition of titanium oxide (reactive magnetron sputtering DC) was effected for 3 minutes in an argon- oxygen mixture at a total pressure of 2.6-2.7 mTorr. The result was a cardboard sheet coloured with light interference colours.
Example 24 A flat carbon steel sample whose surface was de- greased in acetone and activated in sulfamic acid, was pret-reated- -w-i-th a - ca-t-aphoret-ic organic 1-ayer.- A -layer- of zirconium was deposited on this layer with the magnetron sputtering technique. The zirconium film having a thick¬ ness of a few micrometers was electrochemically coloured.
Example 25 A glazed stoneware tile was coated with a layer of titanium by means of the cathodic arc deposition tech¬ nique. The coated tile was treated in an air oven for colouring by thermal oxidation. After about ten minutes at 3700C, a yellow-coloured layered was obtained.
Example 26 A hollow ball, having a diameter of 12 cm, consist¬ ing of a mixture of polyester resin and alabaster powder was coated with a layer of titanium by means of the mag¬ netron sputtering technique. The deposition lasted 1 min- ute at 1.72 mTorr of argon pressure. At the end of the titanium deposition a layer of titanium oxide was depos¬ ited with the reactive magnetron sputtering technique, using an argon/oxygen mixture at 2.5-2.7 mTorr of total pressure. The deposition lasted 3 minutes: the result was a surface coated with titanium oxide and characterized by typical interference colours .
Example- 27 -- - A flat chromium-plated sample (10 cm x 10 cm x 0.5 cm) was degreased with acetone and activated in diluted sulfuric acid at 3% for a few minutes at room tempera¬ ture. The surface was coated with an organic layer hard¬ ened with UV rays. A metallic nickel layer was deposited on this organic layer using the procedure of Example 1. A titanium layer was deposited on the composite barrier layer (organic + nickel) with the magnetron sputtering technique. Titanium oxide was deposited on this layer by reactive sputtering. A sample with a coloured surface was produced. Example 28 A sample of polyacrylonitrile organic fibre was sub¬ jected to coating with a barrier layer of the metallic type, followed by coating with titanium and finally elec- trochemical colouring. The surface of the fibre was acti¬ vated with a commercial solution of Sn/Pd by immersion at room temperature for 2 minutes. Metallization was then effected by the autocatalytic deposition of copper in a bath based on formaldehyde at room temperature for 10 minutes. The deposition cycle of the titanium layer on the copper-coated fibre was based on an initial activa¬ tion phase with the use of an ionic source: the activa¬ tion- treatment- lasted 5 minutes -at 1.-9 -mTorr of—-argon pressure at a voltage of 1.4 kV. This was followed by the coating phase by means of the magnetron sputtering tech¬ nique: the coating treatment lasted 20 minutes at an ar¬ gon pressure of 1.9 mTorr; the sputtering current was 6.6 A. The result was a deposit in the order of a micrometer with a dark grey shiny appearance. The titanium layer was coloured by means of anodic oxidation in a solution of phosphoric acid.
Example 29 A sample of polyacrylonitrile organic fibre was sub- jected to coating with a barrier layer of the metallic type, followed by coating with titanium and finally elec¬ trochemical colouring. The surface of the fibre was acti¬ vated by immersion at room temperature for 2 minutes in a commercial solution of Sn/Pd. Metallization was then ef- fected by the autocatalytic deposition of copper in a bath based on formaldehyde at room temperature for 10 minutes. A second activation of the copper base was sub¬ sequently effected with a commercial solution of Sn/Pd by immersion at room temperature for 2 minutes. Metalliza- tion was then effected by the autocatalytic deposition of an Ni-P alloy in the composition bath with the following characteristics: nickel acetate 0.12 M, sodium hypo- phosphite 0.32- M, lactic acid--0.5- M, pH 4^7, -opera-ting- temperature 850C. The nickel-phosphorous deposition was carried out for 30 minutes, producing a deposit having a thickness of 10 micrometers. The deposition cycle of the titanium layer was based on an initial activation phase with the use of an ionic source: the activation treatment lasted 5 minutes at 1.9 mTorr of argon pressure, at a voltage of 1.4 kV. This was followed by the coating phase by means of the magnetron .sputtering technique: the coat¬ ing treatment lasted 20 minutes at an argon pressure of 1.9 mTorr; the sputtering current was 6.6 A. The result was a deposit in the order of a micrometer with a dark grey shiny appearance. The titanium layer was coloured by means of anodic oxidation in a solution of phosphoric acid, at a voltage of 20 V, obtaining a violet/blue- coloured layer of titanium oxide.