SUBSTRATE

BACKGROUND OF THE INVENTION

1. Field of the Invention.

The present invention relates to a new method for treating a surface of a substrate in order to confer protection against mechanical, thermal and chemical aggresion and, more particularly the invention refers to a method for applying, in sequence, at least two protective layers by well known techniques such as ionic implantation and plasma-enhanced chemical vapor deposition (PECVD) and a third layer such as one made of an epoxi .

2. Description of the Prior Art. It is well known that corrosion is a relevant issue in many areas of different activities. Particularly in the industry, there are many machine pieces and other components exposed to different corrosive agents and, particularly in the petroleum industry and oilwells the equipments and particularly tubings, are extremely exposed to corrosion and/or erosion caused by the oil, gases, water and rocks involved in this activity. These corrosive effects are dramatically increased specially in the presence of water at the high temperatures and pressures . The above mentioned problems in tubes, pipes and casings is a concern and has been faced with different solutions in existing repairing or recycling plants, and others have been proposed in literature. These oil filed equipments are made of ferrous materials, generally normal carbon steel, that are dramatically attacked under the working conditions and this cause this equipment to be replaced in short periods of time.

Some solutions have been tested to protect the pipes against the above cited corrosive conditions and to repair pipings already damaged under a period of service. Among these attempts it is well known to provide a liner or cover by applying a polymer or a plastic material, by spray, blowing and the like, in order to form a layer resistante to chemical and mechanical erosion. While there are many good materials which are employed as liners, these layers are not enough to resist such main erosion agents. The continuous impacts against the inner surface of a casing in an oilwell provoques cracks and fissures permitting the fluid circulating through the casing reach the inner surface of the casing to corrode it. This is due, among other causes, to the lower adherence power between the liner, generaly an epoxi resin, and the casing surface, the substrate. Even if the epoxi layer were cohesive with the substrate, at last, the substrate surface is not well prepared to resist the fluid corrosion affect.

It would be therefore very desirable to have a new multilayer protection and method for applying the same in a substrate subject to corrosion and/or erosion conditions of service, wherein the protecting liner being capable of cohesively resisting the mechanical aggresion as well as the corrosion and erosion preventing the surface of the substrate from being exposed to such aggresive conditions.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a new process for treating a substrate in order to have at least a surface thereof protected by at least a bi- layer formed by plasma-enhanced chemical vapor deposition (PECVD) , deposited in the surface of the substrate in two different steps, and a layer of a polymer, a resin and the like applied in the bi-layer.

It is still another object of the present invention to provide a method for the formation of an anti- corrosive layer in a substrate and substrate treated with the method, wherein the substrate has improved mechanical and corrosion resistance and the method comprising the steps of forming a first layer and a second layer on the substrate by plasma-enhanced chemical vapor deposition (PECVD) with the substrate being at temperature, when forming the first layer, different from the temperature under which the second layer is being formed.

It is a further object of the present invention to provide a method for the formation of an anticorro- sive layer in a substrate, comprising at least the steps of, in sequence: a) forming a first layer on the substrate by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a first temperature;

b) forming a second layer on the first layer by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a second temperature lower than said first temperature, and

c) forming a third layer by applying a mechanical-resistant anticorrosive material on the second layer.

It is a further object of the present invention to provide a substrate having at least one surface thereof protected by a multi -layer protection comprising at least: a) a first layer on the substrate applied by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a first temperature;

b) a second layer on the first layer applied by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a second temperature, and

c) a third layer formed of mechanical-resistant anticorrosive material on the second layer.

The above and other objects, features and advan- tages of this invention will be better understood when taken in connection with the accompanying drawings and description .

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example in the following drawings wherein:

Figure 1 shows a spectrogram of the first layer of a protective multilayer according to the invention, obtained by Fourier Transfom Infrared (FTIR) Spectroscopy, with the layer formed at 500 °C and without methane, and

Figure 2 shows a spectrogram of the second layer of a protective multilayer of the invention, also obtained by Fourier Transfom Infrared (FTIR) Spectroscopy, wherein the layer was obtained at room temperature .

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring in detail to the invention, the same refers to a method or process for treating a substrate, preferably a ferrous based material and more preferably a steel made element, and the invention is preferably applied to the oil field for treating tubular members such as tubings, piping, casings, and similar items employed in the oil industry, however the method of the invention, while described in particular connection to a particular industry and/or field the same may be applied to any equipment, and pieces where corrosion, mechanical and chemical resistance is an issue.

More particularly, the invention refers to a method for the formation of an anticorrosive , mechanical and chemical resistant multi-layer in a substrate, such as a piping, and preferably the inner surface of the piping. The method, according to the invention, comprises at least the steps of: a) forming a first layer on the substrate by plasma-enhanced chemical vapour deposition (PECVD) with the substrate at a first temperature;

b) forming a second layer on the first layer by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a second temperature lower than said first temperature, and

c) forming a third layer by applying a mechani- cal-resistant anticorrosive material on the second layer .

According to the teachings of the invention, the first temperature at which the first layer is formed will be between about 300 °C to about 700 °C, preferably at about 500 °C, and the second temperature of the substrate is between about 0°C to about 100 °C and preferably at room temperature . The first layer and the second layers, forming together a bi- layer, are formed by (PECVD) plasma- enhanced chemical vapor deposition of organosilicon precursors, whereby the both layers are formed of a compound of the formula general Si _x O _y C _z . More preferably, the organosilicon precursors are Tri metil silane (CH3)3 SiH; Tetra metil silane (CH3)4 Si; Hexa metil disiloxane (Me3Si)2-0; Hexa metil disilazane (Me3Si ) 2NH ; Di metil di metoxi silane (Me3 ) 2Si (OMe) 2 ; Metil trimetoxi silane (CH3) Si (OCH3) 3 ; Tetra metil ciclo tetra siloxane (CH3- SiH-0-)4; Octa metil ciclo tetra siloxane ( (CH3 ) 2 -Si-O- ) 4 ; Tetra etoxi silane Si(OC2H5)4, and/or Tetra metoxi silane Si (OCH3) 4.

The following Table shows a brief of the sequence and parameters for deposition of the first and second layers.

According to the invention, the formation of the first and second layers are made by PECVD, by employing organolsilicon precursors wherein the silanol is produced either in gaseous phase as well as on the substrate. Since the hydrogen bonding is relatively weak, with a substrate temperature high enough, such as higher than 500 °C, that is the first temperature, employed for deposition of the first layer, the Si-OH bond tends to break thus selectively promoting the formation of covalent bonds Si-O-Si, according to reaction : Si - OH + Si - OH Si - O- Si + H ₂ 0

Also according to the invention, the second layer is deposited at a second temperature, lower than the first one, whereby the above disclosed reaction is also carried out but more slowly. Under these conditions, if the rate of deposition or deposition velocity is slow enough, a substantial or complete elimination of the silanol is desirably obtained.

For the complete process the carbon reactions are as follows:

SiOH

8 0 Si-O-Si + 2 C0 ₂ + 3H ₂ 0

The ≡SiCH3 is never eliminated in its entirety because the carbon provides the necessary elasticity to the covering.

The first and the second layer formed according to the teachings of the invention have been analized by Fourier Transform Infrared (FTIR) spectroscopy and the results may be seen in the charts of Figures 1 and 2. A big difference may be observed between the functional groups of the first layer, that has the one formed at a temperature above 500 °C. This layer actuates as a link or anchorage between the substrate and the second layer which will operate as a covering, layer or liner for anticorrosive protection. This second layer, as it will be explained below, will also form an anchoring layer for receiving a third layer of a mechanical-resistant and/or anticorrosive material such as an epoxi .

The second layer is preferably deposited at room temperature and methane may be added as a second reagent gas. The resulting compounds may be observed in the FTIR spectroscopy for layer obtained by both processes.

Also according to the invention, and as indicated above, a third layer is applied onto the second layer by a step of forming a third layer by applying a mechanical-resistant anticorrosive material in the second layer. The mechanical-resistant anticorrosive material preferably comprises a polymeric material and more preferably an epoxi resin that may be applied at room temperature, preferably between about IOC and 40 °C. The third layer, that is the outermost layer, will provide the necessary mechanical protection and also it may provide an anticorrosive protection in addition to the protection already provided by the second layer. Alternatively, and also according to the teachings of the invention, the method preferably comprises the additional step of forming a base layer by ionic implantation in the substrate. This step is carried out before the step of forming the first layer. More preferably, the ionic implantation consists of the implantation of an element selected from the group consisting of N2 , C2 , Si, Cr, or others capable of modifying the structure of the substrate of the material and thus its properties. Any convenient ion implantation equipment may be employed, typically consisting of an ion source, where ions of the desired element are produced, an accelerator, where the ions are electrostatically accelerated to a high energy, and a target chamber, where the ions impinge on a target, which is the material to be implanted. According to the invention, Nitrogen or other ions can be implanted into a tube, a casing, a tool and any other metal or steel target . The structural change caused by the implantation produces a surface compression in the steel, which prevents crack propagation and thus makes the material more resistant to fracture. The chemical change can also make the tool more resistant to corrosion. Ionic implantation is a well known technique and information about the same may be obtained from the publication Lasorsa, P-J. Morando, A. Rodrigo, "Effects of the plasma oxygen concentration on the formation of SiOxCy films by low temperature PECVD" Surface and Coatings Technology 195, p42-47, (2005). The bi-layer covering formed by the first and the second layer deposited by PECVD will act as an anchorage surface between the base layer, or ion implanted substrate, and the third layer made of epoxi or other polimeric liner. The bi-layer will also form an anticorrosive intermediate layer or barrier. The process of the invention may be carried out in any metal substrate but it has shown effective results in oil field casing and tubes and specially in the covering of the internal surface of these tubular members .

Therefore, according to another aspect of the invention, a substrate having at least one surface thereof protected by a multi- layer protection formed by the above described process is also provided. Thus, the substrate comprises at least a) a first layer on the substrate applied by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a first temperature; b) a second layer on the first layer applied by plasma-enhanced chemical vapor deposition (PECVD) with the substrate at a second temperature, and c) a third layer formed of mechanical-resistant anticorrosive material in the second layer.

As already disclosed above in connection to the method of the invention, the first and second layers are formed by plasma-enhanced chemical vapor deposition (PECVD) of organosilicon precursors which may be selected from the group consisting of Tri metil silane (CH3)3 SiH; Tetra metil silane (CH3)4 Si; Hexa metil disiloxane (Me3Si)2-0; Hexa metil disilazane (Me3Si ) 2NH ; Di metil di metoxi silane (Me3 ) 2Si (OMe) 2 ; Metil trimetoxi silane (CH3 ) Si (0CH3 ) 3 ; Tetra metil ciclo tetra siloxane (CH3 -SiH-0- ) 4 ; Octa metil ciclo tetra siloxane ( (CH3) 2-Si-O-) 4; Tetra etoxi silane Si(OC2H5)4, and/or Tetra metoxi silane Si(OCH3)4. The above mentioned first temperature is between about 300 °C to about 700 °C, preferably 500 °C, and said second temperature is between about 0°C to about 100 °C, preferably room temperature. Alternatively, the substrate may comprise a base layer applied by ionic implantation of an element selected from the group consisting of N2 , C2 , Si, Cr, or others capable of modifying the structure of the substrate of the material and thus its properties. Finally, the substrate of the invention may be any metal member, preferably made of steel and more preferably tubular members, wherein the treated surface may be an inner surface of the member.

While preferred embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined in the appended claims.