KLOTZ BRIAN (US)
WO2016148967A1 | 2016-09-22 |
US20060266438A1 | 2006-11-30 | |||
US20150184303A1 | 2015-07-02 | |||
US20150090154A1 | 2015-04-02 | |||
US20200123070A1 | 2020-04-23 |
Claims 1. A process for forming on a corrodible substrate a corrosion-resistant multi-ply coating comprising: applying an aluminum-containing silicate slurry onto the surface of the substrate and heating the deposited slurry to form a cured composite of an aluminum-containing silicate basecoat that is not electrically conductive, optionally repeating the aforementioned step to form a thicker multi-ply coating; applying an initial solution of trivalent aluminum and phosphate ions (Al+3PO4) to the surface of said basecoat and heating the substrate that has thereon said solution to form a cured ply comprising a composite that is not electrically conductive; mechanically working the surface of the composite to form a modified composite which is in electrically conductive form; and applying to the surface of the modified composite an additional solution of trivalent aluminum and phosphate ions (Al+3PO4), the composition of which may be the same as or different from said initial solution; and heating the modified conductive coated surface having thereon said additional solution under conditions which cure it to form said multi-ply coating which is not electrically conductive. 2. A multi-ply coating prepared by the process of Claim 1. 3. An article that is coated with the multi-ply coating of Claim 2. 4. A process for forming on a corrodible substrate a corrosion-resistant multi-ply coating comprising applying to an aluminum silicate surface which is not electrically conductive and which is hereafter referred to as a basecoat: (A) an initial solution of trivalent aluminum and phosphate ions (Al+3PO4) and heating said surface that has thereon said solution under conditions which form a cured ply (hereafter “composite”) which is not electrically conductive; (B) mechanically working the surface of the composite to form a modified composite which is in electrically conductive form; and (C) applying to the surface of the modified composite an additional solution of trivalent aluminum and phosphate ions (Al+3PO4), the composition of which may be the same as or different from said initial solution; and (D) heating the modified conductive coated surface having thereon said additional solution under conditions which cure it to form said coating which is not electrically conductive. 5. A multi-ply coating prepared by the process of Claim 4. 6. An article that is coated with the multi-ply coating of Claim 5. 7. A process for preparing a corrosion-resistant coating composition comprising adding trivalent chromium and nitrate to a suitable carrier. 8. An article that is coated with the composition of Claim 7. 9. A process according to Claim 1 wherein one or both of said initial solution and said additional solution contain trivalent chromium and nitrate. 10. A process according to Claim 9 wherein said initial solution contains trivalent chromium and nitrate. 11. A process according to Claim 9 wherein said additional solution contains trivalent chromium and nitrate. 12. A process according to Claim 9 wherein both of said solutions contain chromium and nitrate. 13. A process according to claim 1 wherein said silicate slurry comprises sodium silicate and lithium silicate. 14. A process according to claim 13 wherein said slurry includes also polysilicate. 15. A multi-ply coating prepared by the process of claim 13 or claim 14. 16 An article that is coated with the multi ply coating of claim 15 17. A process according to claim 1 wherein said initial solution includes also Mg ion and has a pH of greater than 1.5. 18. A process according to claim 17 wherein said pH is greater than 2.5. 19. A process according to claim 9 wherein said initial solution or said additional solution contains a polymeric resin. 20. A process according to claim 19 wherein said resin is polytetrfluoroethylene or silcones in water. |
EXAMPLES There are described hereafter three examples which are exemplary embodiments of the present invention. All of the compositions described in the examples are Cr +6 Free. EXAMPLE 1 In brief, this example describes the production of a multi-ply coating system in which carbon steel coupons were treated sequentially to the following four basic steps: (1) the formation of an aluminum-containing silicate basecoat that was not conductive; (2) the formation on the surface of the basecoat of an initial trivalent aluminum-phosphate coating (Al +3 PO 4 ) that was not conductive; (3) the burnishing by mechanically working the surface and the Al +3 PO 4 coating to convert it to a conductive form; and (4) the formation on the conductive coasting of step (3) hereof of a non-conductive coating comprising Al +3 PO 4 . The amounts of the ingredients of the coating compositions are given in wt. % based on the total weight of the compositions unless stated otherwise. Two sizes of carbon steel coupons were selected for this example. The smaller panel measured 2” x 3.5” x 0.32” (51 mm x 89 mm x 0.8 mm) and the larger one measured 3” x 5” x 0.32” (76 mm x 127 mm x 0.8 mm). Both sizes of these coupons will be referred to hereinafter as “Panel 1”. The panels were heated for at least 15 minutes at 650°F (345°C) to burn away any oils and then blasted with 120-grit brown aluminum oxide at 80 psi (650 kPa) in a suction blast cabinet. Residual blasting media was blown from blasted surfaces with clean compressed air. Step (A) — Apply Aluminum-Silicate Basecoat An aluminum-silicate slurry was applied to the cleaned and blasted steel coupons. The slurry was like that described in U.S. Patent No.9,739,169. It comprised fine aluminum powder dispersed in an aqueous liquid bonding solution of sodium silicate and lithium silicate. a) sodium silicate 6.9% ratio of silica (SiO2) to sodium oxide (Na2O) of 2.5 to 1; b) lithium polysilicate 3.5% ratio of silica (SiO2) to lithium oxide (Li2O) of 10 to 1; c) water; 45.3 % d) amorphous silicon dioxide; and 1.6 % e) aluminum powder, 4.5 to 6.5 microns (average diameter), 42.7% ratio of silicate to aluminum by weight, 0.23 to 1. The aqueous solutions of sodium silicate and lithium polysilicate were first combined with water. Aluminum powder was then blended into the mixture until it all was thoroughly dispersed. The final mixture was screened through a 325-mesh wire sieve. The aluminum-silicate slurry was applied to the coupons using a DeVilbissTM EGHV-531 HVLP air-atomizing siphon spray gun with an E-tip and fluid nozzle with a 1.1 mm opening. Step (B) — Cure Aluminum-Containing Silicate Basecoat Coupons coated with the liquid aluminum-silicate composition described in Step (A) were dried in air, then heat dried at 175°F (89°C) for at least 15 minutes before being baked at 650°F (345°C) for at least 35 minutes to cure the silicate into a solid aluminum-ceramic film. The coupons were removed from the oven and cooled. When the panels had cooled, steps (A) and (B) were repeated to deposit a second aluminum-ceramic layer on the coupons. The two separately cured coats of aluminum-silicate on the coupons were about 2.3 to 3.0 mils (58 to 76 microns) thick. This layer of cured aluminum- silicate was not conductive. In other words, when probes of an ohmmeter were placed one inch (25 cm) apart on the coated surface, no current flowed and no reading registered on the device. Step (C) — Apply to the Non-Conductive Basecoat Cr-Free Al +3 PO 4 Coating Solution A chromium-free dilute aqueous solution of phosphoric acid saturated with trivalent aluminum ion (Al +3 ) was prepared comprising: water 61.5 % 75 % phosphoric acid 34.25 % Aluminum hydroxide 4.25 % (J.M. Huber Corp., Onyx Elite ® 431). Phosphoric acid was added to water and the aqueous solution thereof was heated to about 150°F (66°C). Aluminum hydroxide was then added gradually so that the temperature of the solution never exceeded 190°F (88°C). Stirring was stopped once all aluminum hydroxide had dissolved in the phosphoric acid solution and the mixture was allowed to cool to less than 100°F (38°C). The phosphoric acid solution saturated with aluminum ion contained 34.25% of 75% phosphoric acid, 4.25% of aluminum trihydrate, and 61.50% of water. Magnesium oxide was added to the aforementioned solution to buffer it. The magnesium hydroxide was stirred into the aqueous solution a bit at a time. When the solution had clarified, its pH measured > 2.6 at 76 to 78°F (24.5 to 25.5°C). The buffered solution was passed through a 500- mesh wire screen. Nothing was retained on the sieve. The resulting solution (S1) comprised the following ingredients: Al +3 -phosphate bonding solution, A1 89.3 % magnesium hydroxide 4.7 % water 6.0 % Before this solution was applied to the cured aluminum-silicate basecoat, a blend of organic solvents (84 wt. % propylene glycol monomethyl ether acetate and 16% tripropylene glycol methyl ether) was added to aid wetting. One (1) part solvent by volume was added to ten (10) parts of the solution. A DeVilbiss EGA-503 air-atomizing spray gun with an F-tip (< 0.9 mm diameter opening) and fluid needle was used to apply a thin wet coat of the S1 treatment solution onto the surface of the cured aluminum-silicate basecoat. The solution was sprayed onto the surface in multiple passes until the surface took on a uniform sheen. Any wetness disappeared quickly as the solution S1 soaked into the cured aluminum-silicate basecoat. After the first mist coat of S1 had dried for a few minutes, a second coat was applied until the surface again took on a uniform luster. This was repeated until the surface stayed mostly wet with solution S1 even after sitting for one minute. Step (D) — Heat Cr-Free Aluminum Phosphate Coating Solution The cured aluminum-silicate basecoat that had been treated with solution S1 in step (C) was dried at ambient for at least 5 minutes and then transferred to an oven preheated to 175°F (89°C). After 15 minutes, the set point of the oven was raised to 650°F (345°C) and the coupons which had thereon the cured aluminum-silicate basecoat with absorbed S1 were heated to that temperature and held for 35 minutes to form a solid, cured, modified composite. When the coupons had cooled, conductivity of the modified composite was measured using probes of an ohmmeter as described in Step (B). The surface was not conductive. Step (E) — Mechanical Treatment of the Non-Conductive Modified Composite When the coupons had cooled, the surface of the modified composite deposited in Steps (A) thru (D) was lightly blasted with 240-grit aluminum oxide at 40 psi (380 kPa) in a suction blast cabinet; a process called burnishing. Upon burnishing, the surface of the modified composite became brighter in color and slightly reflective. Impinging burnishing media removed residual cured solution S1 from the surface of the modified composite. Touching to the surface two probes of an ohmmeter held one-inch (25 cm) apart on the surface confirmed that burnishing also lowered the electrical resistance of the surface of the modified composite to merely 0.5 ohm, making the composite coating conductive. Burnishing also compressed the composite slightly, reducing its thickness by roughly 0.2 mils or 5 microns on average. Step (F) — Apply to the Conductive Composite Coating an Additional Coating Al +3 PO 4 Solution A khaki-colored Al +3 PO 4 solution (B1) containing nitrate ions was made as follows: water 117.8 gm 75 % Phosphoric Acid 65.52 gm Aluminum Hydroxide 16.51 gm J.M. Huber Corp., Onyx Elite® 431 Chromium(III) nitrate nonahydrate, 98.5% (solid) 48.52 gm Alfa Aesar, CAS 7789-02-8. The phosphoric acid was added to the water in a glass flask on a combined hot plate/magnetic stirrer. A magnetic stir bar was added. Chromium nitrate crystals were added as the solution stirred. The phosphoric acid-nitrate solution was covered and heated to between 150 o and 160 o F (66 o and 71 o C) while stirring. The crystals dissolved completely in the acid, turning the clear, colorless liquid dark violet-green. Aluminum hydroxide was stirred into the hot solution. It was added incrementally so its temperature did not exceed 190 o F (88 o C). (Dissolution of aluminum hydroxide in the acid is exothermic. If the solution gets too hot, insoluble reaction products form.) After all the aluminum hydroxide had been added, the hot solution was covered and stirred for an hour and a half at 160 o to 170 o F (71 o to 77 o C). Afterwards it appeared clear, but when it had cooled and sat overnight, a fine layer of white powdery aluminum hydroxide covered the bottom of the flask. The mixture was set to stirring again and heated back to 160 o to 170 o F (71 o to 77 o C). After the phosphoric acid, trivalent chromium nitrate and aluminum hydroxide had been stirred for five hours at the elevated temperature, the hot plate was turned off. A 15 ml sample was taken from the hot mixture and placed in a glass vial. The flask was covered again and allowed to stir on the plate as it cooled. No white particulate was seen on the bottom of the glass vial when the solution had cooled to room temperature. When the flask had cooled, its contents were poured through a 635-mesh stainless steel wire sieve. Little if any particulate was captured on the screen, indicating that all the aluminum hydroxide had dissolved in the solution. Properties of the solution at 77 o F measured: pH 0.6 Density (lb./gal.) 10.9 lb./ gal. Viscosity (#2 GE Zahn) 17 sec. The solution contained 25 % by weight solids which were determined by heating the solution for 30 min. at 175 o F and 30 min. at 650 o F. Testing showed that solution B1, made with chromium nitrate as described, contained less than 1 ppm hexavalent chromium, making it Cr +6 Free. Blue, brown and yellow pigments, along with colloidal silica, were added to the additional Al 3 PO 4 solution to make a slurry (T1) that could be sprayed and applied to the grit-burnished conductive composite coating formed in Step (F) of this embodiment of the invention. Solution B1 (Cr +3 / Al +++ -phosphate) 83.2 % colloidal silica 0.85 % (Ludox® SM 30 % solution, W.R. Grace Co.) Cobalt aluminate blue pigment 2.4 % (Shepherd # 214 blue, Shepherd Color Co.) Nickel antimony titanate yellow pigment 9.8 % (Shepherd # 101-C112E yellow, Shepherd Color Co.) Iron titanate brown pigment 3.75% (Shepherd # 10P858 brown, Shepherd Color Co.). After blending for 30 seconds, the slurry T1 was screened through a 500-mesh stainless steel wire sieve. (Essentially no residue was retained on the sieve.) The resulting composition was sprayed onto the burnished surface of the conductive composite using a DeVilbiss EGA-503 siphoning spray gun with an F-tip. Three thin coats were applied, thoroughly drying each between coats, until the surface became uniform in color and remained shiny after it dried. After the coated coupons were dried to the touch, they were transferred to an oven preheated to 175°F (89°C). After 15 minutes, the set point of the oven was raised to 650°F (345°C). The coupons were heated to the set point and held at that temperature for 35 minutes to cure the top coating. The thickness of the finished multi-layer composite coating of this example of the invention ranged from 2.5 to 3.3 mils (78 to 84 microns) on average. The topcoat itself was 0.3 to 0.5 mils (8 to 13 microns) thick and it was not conductive. EXAMPLE 2 In another embodiment of this invention, carbon steel panels were coated with a multi- layered coating system described in Example 1 except for the following differences. In Example 1, the initial Al +3 PO 4 coating solution utilized in Step (C) of Example 1 did not contain trivalent Cr or nitrate and the “additional” Al +3 PO 4 solution contained both trivalent Cr and nitrate. In Example 2 hereof both the initial AL +3 PO 4 solution and the “additional” AL +3 PO 4 solution did not contain trivalent Cr and nitrate. Accordingly, this example demonstrated that the present invention can be used effectively in practicing both the embodiments of Examples 1 and 2. There follows an additional description of information respecting details of Example 2. Two sizes of carbon steel panels were the subject of this example. The smaller panel measured 2” x 3.5” x 0.32” (51 mm x 89 mm x 0.8 mm) and the larger 3” x 5” x 0.32” (76 mm x 127 mm x 0.8 mm). Both sizes of these panels will be referred to hereinafter as “Panel 2”. Both panels were prepared exactly as carbon steel coupons had been prepared for Example 1. The aluminum-silicate slurry applied in Step (A) of this Example was identical to that used in Example 1. Cure times and temperatures in aforementioned Steps (B), (D) and (G) were identical to those used in Example No.1, as were the grit size and blasting pressure used to burnish the treated basecoat. However, in Example 2 hereof a khaki-colored solution completely free of both chromium and nitrate ions (“T2”) was prepared by adding to the Al +3 PO 4 ingredients blue, brown and yellow pigments, and also fumed silica identified below: Solution S1 83.2 % Fumed silica 0.85 % ( Aerosil 200, Evonik Corp.) Cobalt aluminate blue pigment 2.4 % ( Shepherd # 214 blue, Shepherd Color Co.) Nickel antimony titanate yellow pigment 9.8 % ( Shepherd # 102-C112E yellow, Shepherd Color Co.) Iron titanate brown pigment 3.75 % (Shepherd # 10P858 brown, Shepherd Color Co.). This mixture was blended for 30 seconds and then screened through a 500-mesh stainless steel wire sieve. (Little residue was retained on the sieve.) The blend of organic solvents used in Step (C) of Example 1 (84 wt. % propylene glycol monomethyl ether acetate and 16% tripropylene glycol methyl ether) was added to this screened, khaki-colored slurry. As in Example 1, one (1) part solvent by volume was added to ten (10) parts of the topcoat made from solution S1. The khaki mixture was sprayed onto the surface of the burnished, conductive composite coating using a DeVilbiss EGA-503 siphoning spray gun with an F-tip. Three thin coats were applied, thoroughly drying each between coats, until the color and luster of the surface was uniform. When dry to the touch, the panels topcoated with T2 were baked for 15 minutes at 175°F (89°C). The temperature of the oven was then raised to 650°F (345°C) and held for 35 min. to cure the completely chromium-free khaki topcoat. The thickness of the finished multi-layer composite coating was about 2.6 to 3.0 mils (66 to 78 microns) on average. The topcoat itself was about 0.3 to 0.5 mils (8 to 13 microns) thick. The topcoated and cured surface was not conductive. EXAMPLE 3 This example demonstrates that the multi-ply coating system that was formed on carbon steel panels as described in Example 2 is similarly effective when applied to a stainless steel substrate typical of that used to manufacture turbine engine components. In this example, the multi-ply coating system described in Example 2 was applied to two panels made of JetheteTM martensitic stainless steel. (One panel measured 38 x 70 x 1.5 mm. The other panel measured 70 x 150 x 1.5 mm.) and comprised Jethete which is a 12% Cr alloy steel. It is typical of those alloys used to make compressor blades and vanes for gas turbine engines. The stainless steel panels were prepared and coated in the same way as the carbon steel panels identified as Panel 2 in Example 2. The two Jethete panels coated in this example are referred to hereafter as Panel 3, irrespective of their size unless stated otherwise. Panel 3 panels were evaluated in 1) hot deionized (DI) water and 2) in 5% neutral salt fog. Panel 3 panels were partly immersed in 140 mL of hot DI water in a glass beaker. The beakers and its contents were sealed with plastic films and the beakers placed in an oven preheated to 80 o C and allowed to rest at that temperature for 100 hrs. After 100 hrs. in the hot DI water, the multi-ply coatings were largely unaffected, showing no blisters. Though some white material leached from the exposed or outer surface of the multi-ply coating, the water remained clear throughout the test. The conditions of the panels and hot water remained unchanged through 500 hrs., at which time the test was terminated. With respect to the salt fog test of the larger panel, an "X" was scribed through the outer surface of the multi-ply coating on one side of the larger Panel 3 panel. After the edges of the panel had been waxed, it was placed in a 5% neutral salt fog cabinet operating per ASTM B117 as salt fog condensed on the scribed surface. Through 3000 hrs. in 5% neutral salt fog per ASTM B117, no red rust was observed anywhere on panel 3; the multi-ply system that was used to form the Panel 3 hereof remained tightly adhered on the front and back of the panel. With reference to the three examples hereof, Example 1 and Example 2 are distinguishable in that the Al +3 PO 4 solutions used in the multi-ply coating system of the present invention are different; Example 3 hereof distinguishes over Examples 1 and 2 in that the substrate coated in Example 3 is different from the substrates coated in Examples 1 and 2. Various tests have been performed on the three multi-ply embodiments that have been made using the coating system of the present inventions. Such tests have included evaluations of the corrosion-resistant and other properties of the embodiments. The results of such tests have revealed that, relative to prior art developments, properties of embodiments of the present invention possess improved properties, including in various cases, significantly improved properties. And uniquely significant is that such properties are achieved by the use of compositions and techniques of application that are environmentally acceptable – no need to practice the present invention by having to use, for example, toxic hexavalent chromium. EXAMPLE 4 This is an example of the present invention and is identical to that of Example 1 except that the sequence of Steps (A) and (B) – that is, the application and cure of the aluminum-silicate basecoat layers – differs in this example. Example 1 describes an embodiment of the present invention that is a multi-ply coating utilizing two coats of aluminum-silicate basecoat that are sprayed and cured separately. However, it is widely known in the art to spray a single coat of an aluminum-filled chromate/phosphate slurry onto a prepared surface in order to allow that layer to dry in air and then to spray on a second coat of slurry to wet the coated surface a second time. After that second coat has dried in air again, it is known to heat dry and cure the coating at an elevated temperature. Applying two coats of basecoat with a single heat cure is often known in the art as “wet-on-wet” application. This example utilizes a wet-on-wet application of the same aluminum-silicate basecoat used in previous Examples 1, 2 and 3; it shows that the hot water stability and corrosion-resistance of the present multi-ply coating system incorporating a wet-on-wet basecoat is comparable to that of a system in which the basecoat is applied in two separately cured coats. As was the case in Examples 1 and 2, carbon steel (CS) panels coated for this example were of two different sizes. The smaller panel (referred to hereinafter as a “small CS panel”) measured 2” x 3.5” x 0.32” (51 mm x 89 mm x 0.8 mm) and the larger one (“large CS panel”) measured 3” x 5” x 0.32” (76 mm x 127 mm x 0.8 mm). Two coats of aluminum-silicate slurry were applied to grit-blasted panels in the wet-on-wet manner described above. One small CS panel and two large CS panels are referred to as “Panel 4” hereafter. A single coat of aluminum-silicate slurry like that disclosed in U.S. Patent No.9,739,169 was applied to the Panel 4 panels as in Step (A) of Example 1. After the wet coat of aluminum-silicate had dried, a second coat of the same slurry was sprayed onto the panels until a uniformly wet finish was again achieved. After drying in air, the panels were dried for at least 15 minutes at 175 o F (79 o C) before being cured at 650 o F (343 o C) for 30 minutes as in Step (B) of Example 1. The Al +3 PO 4 bonding Solution S1 which is described in Example 1 was applied to the cured wet-on-wet aluminum-silicate basecoat on the Panel 4 panels in accordance with Step (C) as described in Example 1. (No solvent was mixed with Solution S1 before it was sprayed onto the cured aluminum-silicate basecoat as had been done in Example 1.) The treated, cured wet-on-wet coat of aluminum-silicate basecoat was then baked at 650 o F (343 o C) as in Step (D) of Example 1. The cured aluminum-silicate composite was lightly blasted (“burnished”) with 240-grit alumina abrasive grit at 40 psi in a suction blast cabinet as in Step (E) of Example 1. After burnishing, electrical resistance between two probes placed at least 1-inch (25.4 mm) apart on the coated surface measured < 5 ohms. The Al +3 PO 4 topcoat described in Example 1 (hereafter “solution T1”) was applied over the cured, conductive coating, that is, in Step (F) of this example. The topcoat was cured at 650 o F (343 o C) as in Step (G) of Ex.1 to provide a top coated surface that was not electrically conductive. Comparative Example for Hot Water Test, Panel 4-C1 Another small CS panel was cleaned, grit-blasted, and coated with the same materials in the same manner as used for Panel 4 panels except that Steps (C) and (D) were omitted. This comparative example is referred to hereafter as "Panel 4-C1". TABLE Ex.4.A below shows the steps used in the formation of Panels 1, 4, and 4-C1.. TABLE Ex.4.A: Process Steps for Hot Water Test Panels of Ex.4 The properties of Panels 4 and 4-C-1 were evaluated in hot deionized (DI) water. Panel 4 and Panel 4-C1 were sealed in separate beakers partially filled with hot DI water and placed in an oven at 80 o C (176 o F) for 100 hr., as described in Example 1. The multi-ply coating system on Panel 4-C1 blistered above and below the waterline. The coating on Panel 4 was unchanged. No material had leached from the coated surface. No chalky white deposits were observed on the panel or in the water in the beaker. Panel 4 was returned for further testing. When testing was terminated after 1000 hours, the coating on Panel 4 was still tightly bonded everywhere on the panel. The “test” performance of Panel 4 was equivalent to that of Panel 1. Comparative Example for Sacrificial Corrosion Test, Panel 4-C2 Two large CS panels were cleaned, grit-blasted, and coated with the same materials and in the same manner as used for Panel 1, (Example 1). These two comparative examples are referred to hereafter as "Panels 4-C2". Process steps used in the evaluation of the corrosion-resistance of Panel 4 and Panel 4-C2 are shown in TABLE Ex.4.B. below. TABLE Ex.4.B: Process Steps for Corrosion Test Panels of Ex.4 The corrosion-resistance of the above panels was determined using salt fog. An "X" was scribed through the coating layer on one side of Panels 4 and 4-C2 so that the substrate was exposed in the scratch and the panels were placed in a 5% salt fog cabinet per ASTM B-117 for 2500 hr.) The results of the testing showed that there was little difference in the appearance of the four examples of two embodiments of the invention through 1000 hours in salt fog. No red rust had formed on any panels. After 2500 hrs. in salt fog, some red rust was observed in the scribe on one Panel 4 panel and one Panel 4-C2 panel. Apart from slightly more sacrificial white corrosion on panels with wet-on-wet basecoat (Panel 4), there was little difference between the two embodiments of this invention. The tests demonstrated that, for a coating system of this invention, the aluminum-silicate basecoat may be applied either in two layers with a single cure or in two separately cured coats. EXAMPLE 5 This is an example of the present invention involving the coating of carbon steel (CS) panels like those described in Example 1. The steps used in the coating of the panels included the step of overcoating a conductive layer of aluminum-ceramic with a second non-conductive layer of the same material which is a step known in the prior art for Al-chromate/phosphate coatings. It is a step referred to in the formulation of a “Class 3” coating; it was first described in U.S. Military specification, MIL-C-81751B (now inactive) which is incorporated herein by reference. A small carbon steel (CS) panel and a large CS panel were coated with an embodiment of this invention in which the aluminum-silicate basecoat was in the Class 3 condition. These steel panels are referred to hereafter as “Panel 5” panels regardless of size. A single coat of aluminum-silicate slurry like that disclosed in U.S. Patent No.9,739,169 was applied to Panel 5 panels as described in Step (A) Example 1 and then cured at 650 o F (343 o C) as in Step (B) of Example 1. Before a second coat of aluminum-silicate was applied, as described in Examples 1, 2 and 3, a layer of Al +3 PO 4 bonding solution S1 was applied to Panel 5 panels as in Step (C) of Examples 1, 2 and 3. The treated, single coat of aluminum-silicate basecoat was then baked at 650 o F (343 o C) (Step (D) of Example 1 to cure the layer and render it insoluble. The single layer of cured, treated aluminum-silicate composite was lightly blasted (“burnished”) with 240-grit alumina abrasive grit at 40 psi in a suction blast cabinet (Step (E) in Examples 1, 2 and 3). After burnishing, electrical resistance between two probes placed at least 1-inch (25.4 mm) apart on the coated surface measured < 5 ohms. A second coat of aluminum-silicate slurry identical to the first applied in Step (A) was applied over this single conductive layer and then cured at 650 o F (343 o C) (Step (B)). The resulting surface was not electrically conductive. The Al +3 PO 4 topcoat (khaki-colored) used in Example 1, solution T1, was applied over this cured, non-conductive coating in Step (F) in this example. The system was cured at 650 o F (343 o C) in Step (G) to provide a top coated surface that was not electrically conductive. Comparative Example, Panel 5-C1 As a comparative example, identical carbon steel panels of both sizes, were cleaned, grit- blasted, and coated with the same materials in the same manner as described above except that Steps (C) and (D) were omitted. These comparative examples are referred to hereafter as "Panel 5-C1" regardless of size. TABLE Ex.5 below shows the steps used in the formation of the panels of Ex.1, Panel 5, and P-5-C1. TABLE Ex.5: Coating Process for Panels of Example 5 As in other examples, the above panels were compared in 1) hot deionized (DI) water and 2) corrosion-resistance in 5% salt fog. As to the hot water stability test, the coating Panel 5 of the present invention was largely unchanged after 100 hrs. partly immersed and sealed in hot water. No material had leached from the surface. No chalky white deposits were observed on the panel. The water had remained clear. By contrast, the multi-layered coating system of comparative example Panel 5-C1 had blistered and peeled below the waterline. Material that had exuded from the coating clouded the water in the beaker. Panel 5 was further evaluated in the hot water test. After 500 hours, most of the water in the beaker had evaporated due to a breach in the seal, leaving a white stain on the back of the panel. The beaker was refilled, its seal restored, and the beaker was returned to test for another 700 hours at which time the test was terminated. The water remained clear through the balance of the test and there was no other change in the condition of the coating on Panel 5. With respect to the evaluation of the corrosion-resistance, an "X" was scribed through the coating layer on one side of each large CS panel, so the substrate was exposed. The scribed, coated panels were then placed in a 5% neutral salt fog cabinet operating in accordance with ASTM B- 117 so salt fog condensed on the scribed face of each. The multi-ply coatings remained tightly bonded to the front and backs of Panel 5 and on Panel 5-C1 through 3000 hours in salt fog. There was no red rust on either panel. There was less white sacrificial aluminum corrosion on Panel 5 than on Panel 5-C1. The test was terminated at 3000 hr. EXAMPLE 6 In another embodiment of the present invention, a multi-layered coating system was formed on carbon steel (CS) panels in a manner that was identical to that described in Example 1, except that a different aluminum-silicate basecoat slurry (“BC2”) was used in Step (A). Two small CS panels and two large CS panels (Ex.1) were coated with and were prepared exactly as panels were prepared and coated per Steps (A) through (G) used in Example 1, except that, in this example, the aluminum-silicate basecoat utilized a binder of lithium- and potassium- silicate instead of binder made with sodium- and lithium-silicate used in Example 1. Panels coated with this embodiment of the invention will be referred to hereinafter as “Panel 6” panels, regardless of size. The aluminum-silicate basecoat comprises a slurry of fine aluminum powder in a lithium modified potassium-silicate binder as follows. Aluminum-Silicate Basecoat Slurry, BC2 Wt. % a) Aluminum Powder 36.0 % (Eckart 407 grade air atomized aluminum powder) Average particle size: 5 microns b) Aqueous Lithium-Potassium Silicate 41.2 % (PQ Corp. LITHISIL 829 - 29.7 % silicate by weight) c) Water 22.8 % Ratio of Silicate to aluminum by weight: 0.29 to 1.0 The above ingredients were blended at high speed. When cool, the slurry was screened through a 325-mesh wire sieve. The slurry is like that disclosed as Formulation 58A in TABLE 1 of US Patent 9,017,464 (Belov ‘464). This aluminum-silicate slurry was applied to panels in the same manner described in Step (A) of Example 1. After application, the aluminum-filled lithium-potassium-silicate basecoat was dried and cured at 650 o F (343 o C) per Step (B) of Ex.1. In Step (C) of this example, the cured basecoat on Panel 6 was treated with solution S1ƍ. Treatment Solution, S1ƍ Wt. % a) Al +3 PO 4 bonding Solution S1 of Ex.1 96.5 % b) Shepherd #10C112E Yellow pigment 1.6 % c) Shepherd #1 Black pigment 1.9 % Once Solution S1ƍ had been applied to the cured basecoat and allowed to dry in ambient air, the treated panel was cured as in Step (D) of Example 1. After being burnished to < 5 ohm electrical resistance as in Step (E) of Ex.1, the Panel 6 panel was overcoated with Al +3 PO 4 topcoat solution T1 as in Step (F) of Ex.1 before being cured per Step (G) of that example. Comparative Example 1, Panel 6-C1 One small CS panel and two large CS panels were cleaned, grit-blasted, and coated with the same materials applied to the Panel 6 panels in like manner except that Steps (C) and (D) were omitted. These comparative examples are referred to hereafter as Panel 6-C1, regardless of size. Comparative testing is reported in Table 6 Ex.6 below. Comparative Example 2, Panel 6-C2 A small CS panel was cleaned, prepped, and coated with the aluminum/lithium- and potassium-silicate basecoat described above. After curing, this basecoat was burnished with 240- grit abrasive in the same manner as used in Step (E) for Panel 6. After Step (E), electrical resistance of the burnished aluminum-ceramic surface on Panel 6-C1 measured less than 0.5 ohm (electrically conductive) between two probes of an ohmmeter placed one-inch (25 cm) apart on the burnished surface. Comparative Example 3, Panel 6-C3 Another small CS panel was cleaned, prepped, and coated with the aluminum/lithium- and potassium-silicate basecoat described above and then cured at 650 o F as in Step (B) of Example 1. TABLE Ex.6 shows the steps used in the formation of Panels 6, 6-C1, 6-C2, and 6-C3. TABLE Ex.6: Coating Process for Panels of Example 6 Comparative examples 6-C1, 6-C2, and 6-C3 were subjected to hot water stability testing. The test results are reported below in Table Ex. 6.A below which summarizes the conditions of the panels at the end of this exposure. The multi-ply coating on Panel 6 incorporating Al/lithium-potassium-silicate basecoat (an embodiment of the present invention) remained stable through 100 hr. in hot DI water. It did not blister or discolor. Panel 6 was returned to the test and remained unchanged through 1000 hrs. in hot DI water, at which time the test was terminated. TABLE Ex.6.A: Condition After 100 Hrs. in Hot DI Water Panels 6, 6-C1, 6-C2 and 6-C3 spent nearly 100 hrs. in an oven at 80 o C (176 o F) sealed in a beaker partially filled with hot DI water. As sprayed and cured, lithium-potassium silicate basecoat alone (Panel 6-C3) was little affected by 100 hours in hot DI water, apart from some rust at the waterline. However, the basecoat that had been made electrically conductive by light abrasive blasting blistered badly in hot water. Burnished basecoat on Panel 6-C2 wrinkled badly above the waterline and blistered where it was immersed. The multi-ply coating on Panel 6-C1 comprising burnished BC-2 basecoat with an overcoat of Topcoat T1 (Panel 6-C1) also wrinkled and blistered. Table Ex.6.B below reports the results of evaluating the corrosion-resistant properties of the panels. The evaluation consisted of scribing large Panels 6, 6-C1 and 6-C2 and then placing them in 5 % neutral salt fog per ASTM B-117 as had been done in previous examples. TABLE Ex.6.B: Condition of Scribed Panels After 5% Salt Fog With reference to TABLE Ex. 6.B above, coatings on Panels 6-C2 and 6-C1 blistered within the first week in salt fog. (Red rust also appeared on one of the 6-C2 panels.) In contrast, there were no blisters nor red rust of Panel 6 of the present invention through 1500 hrs. in salt fog. There was observed, however, somewhat more white sacrificial corrosion on Panel 6. EXAMPLE 7 In another embodiment of the present invention, a multi-layered coating system was formed on carbon steel (CS) panels in a manner that was identical to that described in Example 6 except that only a single coat of aluminum-silicate slurry was used in Step (A). A small CS panel and two large CS panels were coated in an embodiment of this invention in which the panels were prepared exactly as the carbon steel panels were prepared in Example 6 and were coated per Steps (A) through (G) as in that example except that only one coat of basecoat was applied to these panels which will be referred to hereinafter as “Panel 7” panels regardless of size. Comparative Example Panel 7-C1 One small CS panel and two large CS panels were cleaned and grit-blasted as was used in the coating of the Panel 7 panel except that Steps (C) and (D) were omitted. The comparative examples are referred to hereafter as “Panel 7-C1”. The steps used in the formation of the multi- ply coatings on Panels 7-C1 and Panel 7 panel and also on the Panel 6 panel of Example 6 are shown in TABLE Ex.7 below. TABLE Ex.7: Coating Process for Panels of Example 7 As in prior examples, stability of the multi-ply coatings on Panels 7 and 7-C1 were compared in the hot deionized (DI) water test described in Example 1. Accordingly, Panels 7 and 7-C1 were partially immersed in hot DI water at 80 o C (176 o F) for 100 hr. After that exposure, the multi-ply coating on Panel 7-C1 had blistered. By comparison, the multi-ply coating on Panel 7, which is an embodiment of the present invention., had not blistered. The conditions of Panels 7 and 7-C1 after 100 hrs. partially immersed in hot DI water at 80 o C (176 o F) are summarized in TABLE Ex.7 below. TABLE Ex.7.A: Condition After 100 Hrs. in Hot DI Water It is noted that the Panel 7 panel remained unchanged through 1000 hrs. in hot DI water at which time testing was terminated. In addition, the corrosion-resistance of the aforementioned coatings system were compared in a 5% salt fog test per ASTM B-117. In this test, an "X" was scribed through the multi-ply coating on one side of each of the large Panel 7 and Panel 7-C1 panels. The scribed panels were placed in a 5% salt fog cabinet operating per ASTM B-117 for 1000 hr. Conditions of the panels are recorded in the TABLE EX.7.B. TABLE Ex.7.B: Condition of Scribed Panels After 5% Salt Fog With reference to the above Table, the multi-ply coating on Panels 7-C1 blistered within the first week in salt fog whereas the multi-ply coating of the present invention on Panel 7 remained tightly bonded on those panels throughout exposure. There was more sacrificial white corrosion on this embodiment of the invention on Panel 7 after 500 hours in salt fog than on Panel 7-C1. However, after 1000 hrs., the blistered comparative coating on Panels 7-C1 showed significant white corrosion and hints of red rust whereas neither rust nor blisters were observed on the Panel 7 coating of this invention. EXAMPLE 8 In another embodiment of the present invention, a multi-layered coating system was formed on carbon steel (CS) panels in a manner that was identical to that described in Example 1 except that a different aluminum-silicate basecoat slurry (“BC3”) was used in Step (A). Whereas the basecoat applied in Example 1 incorporated finely divided aluminum in a sodium-/lithium- silicate binder, the basecoat used in this example contained aluminum powder in a potassium- silicate binder. One small CS panel and two large CS panels were coated in the preparation of an embodiment of this invention. The panels are referred to hereinafter as “Panel 8” regardless of size; the three panels were prepared exactly as the carbon steel panels of Example 1 and were coated per Steps (A) through (G) as in Example 1 except that, in this example, the aluminum- silicate basecoat utilized a binder of potassium-silicate instead of the one made with sodium- and lithium-silicate used in Example 1. The basecoat used in this example comprised the following binder: Al-Silicate Basecoat Slurry, BC3 Wt. % a) Aluminum Powder 31.1 % (Eckart™ 407 grade air atomized aluminum powder) Average particle size: 5 microns b) Aqueous Potassium Silicate (29.1 % silicate by weight) 44.4 % (K 2 O:SiO 2 ratio – 2.50; PQ Corp. KASIL™ 1) c) Water 24.5 % Ratio of Silicate to aluminum by weight: 0.203 to 1.0 The above ingredients were mixed at high speed using a Conn™ blade. This aluminum-silicate slurry was applied to the panels using a spray gun as described in Step (A) of Example 1. The potassium-silicate basecoat was dried and cured per Step (B) as described in Ex.1. Cured panels were treated with Al +3 PO 4 Solution S1ƍ as in Step (C) of Example 5, then cured at 650 o F (343 o C) as in Step (D) of Example 5. After being burnished to < 5 ohm electrical resistance as in Step (E) of Ex. 1, each panel was overcoated with Al +3 PO 4 topcoat solution T1 as in Step (F) of that example before being cured per Step (G) of the example. Comparative Example Panel 8-C1 One small CS panel and two large CS panels were cleaned, grit-blasted, and coated with the same materials applied to the panel of Panel 8 above in like manner except that Steps (C) and (D) were omitted. These comparative examples are referred to hereafter as Panel 8-C1 regardless of size. Comparative Example Panel 8-C2 One small CS panel was cleaned, prepped, and coated with basecoat BC3 as described for the panels of Panels 8 and 8-C1. After curing, the basecoat was burnished with 240-grit abrasive in the same manner as used in Step (E) of Example 1. After Step (E), electrical resistance of the burnished aluminum-ceramic surface on Panel 8-C2 measured less than 0.5 ohm (electrically conductive) between two probes of an ohmmeter placed one-inch (25 cm) apart on the burnished surface. Comparative Example Panel 8-C3 Another small CS panel was cleaned, prepped, and coated with the basecoat BC3 and then cured at 650 o F (343 o C) as in Step (B) of Example 1. TABLE Ex.8 below identifies the steps used in preparing the aforementioned panels. TABLE Ex.8: Coating Process for Panels of Example 8 Stability of each of the four panels was evaluated in the hot deionized (DI) water test described in Example 1. The results of the evaluation are reported in TABLE Ex.8.A below. TABLE Ex.8.A: Condition After 100 Hrs. in Hot Water With reference to the 100 hr. exposure in hot DI water summarized in the Table above, the potassium-silicate bonding solution had leached from the BC3 basecoat coatings on Panels 8-C2 and 8-C3. When those panels dried, the basecoat simply wiped off the steel as loose powder. The Panel 8 panel of the present invention remained stable in hot DI water throughout 100 hrs. The coating did not blister or dissolve. After being inspected at 100 hrs., the Panel 8 panel was returned to the hot water. When the test was terminated after 1000 hrs., the coating on of Panel 8 was still unchanged and was tightly bonded to the substrate. The corrosion-resistant properties of Panels 8, 8-C1, and 8-C2 were compared by scribing those panels and exposing them in 5% neutral salt fog per ASTM B-117. An "X" was scribed through the coating on one side of Panels 8, 8-C1 and 8-C2 and the scribed panels were placed in a 5% neutral salt fog cabinet operating per ASTM B-117 for 1000 hrs. The conditions of the panels are summarized in TABLE Ex.8.B below. TABLE Ex.8.B: Condition of Scribed Panels After 5% Salt Fog With reference to the above Table, red rust appeared on Panels 8-C2 and 8-C1 before even a week had passed in salt fog. Rust covered so much of the surface of the two 8-C2 panels that they were removed from the test cabinet after week (168 hrs.). Rust was limited to scribe lines on Panel 8- C1 through 500 hr. in salt fog, but spread everywhere by 1000 hrs. There was no red rust on Panel 8 of the present invention until after 500 hrs. in salt fog and little after even 1000 hrs. EXAMPLE 9 This example describes an embodiment of the present invention that is identical to that of Example 1 except that a silicone resin was added to the Al +3 PO 4 topcoat solution T1 of Example 1 to create a new topcoat solution for use in Step (F) of this example. Two coats of the aluminum-silicate basecoat slurry used in Example 1 were applied to grit- blasted carbon steel (CS) panels in the wet-on-wet manner described in Example 4. One small CS panel and two large CS panels coated with the embodiment of this invention in this example are referred to as “Panel 9” hereafter regardless of size. The cured aluminum-silicate basecoat was treated with Al +3 PO 4 Solution S1ƍ in accordance with Steps (C) and (D) of Ex. 6. The treated and cured aluminum-silicate basecoat was lightly blasted as in Step (E) of Ex.1 until its electrical resistance measured < 5 ohms between two probes placed at least 1-inch (25.4 mm) apart on the surface. An aqueous solution of a silicone resin, Solution R1, was mixed as follows. Resin Solution R1 Wt. % Water-borne silicone resin (Wacher Silrez MP50E) 91.5 % water 8.5 % A silicone-modified, khaki-colored topcoat, Solution T3, was then mixed as follows. Topcoat Solution T3 Vol. % Resin solution R1 50 % Al +3 PO 4 Topcoat Solution T1 (from Example 1) 50 % In Step (F) of this example, Solution T3 was sprayed onto Panel 9 as had been done in Step (F) of Example 1. Panel 9 was then dried at 175 o F (79 o C) for at least 15 minutes before being heated to 650 o F (343 o C) and held for 30 minutes to cure the topcoat in Step (G) to complete this embodiment of the invention. The finished, top coated surface was not electrically conductive. It was observed that water beaded readily on the surface. Comparative Example for Hot Water Test, Panel 9-C1 One small CS panel and two large CS panels were cleaned, grit-blasted, and coated with the same materials in the same manner as used for Panel 9, except that Steps (C) and (D) were omitted. These comparative examples are referred to hereafter as "Panel 9-C1", regardless of size. TABLE Ex. 9 below identifies and summarizes process steps used in preparing Panel 9 that is an embodiment of the present invention and that of the comparative multi-ply example (“Panel 9-C1”). TABLE Ex.9: Process Steps for Panels for Ex.9 With reference to Table 9, a difference between Panels 9-C1 and Panels 9 became apparent even before preparation of the panels was completed. Soon after a smooth, glossy, wet coat of the topcoat, Solution T3, had been applied to Panel 9-C1, bubbles began to form in the wet topcoat. Some of these bubbles “inflated” to more than 1 mm in diameter. The bubbles eventually burst during heat cure leaving craters in the topcoat film. Solution T3 did not bubble when applied to the treated and burnished basecoat on Panel 9. Finished surfaces were not electrically conductive even when probes were placed in craters left in the topcoat where bubbles had broken on Panel 9-C1. The small CS panels, Panel 9 and 9-C1, were subjected to the hot water stability test described in Example 1. After 100 hrs. sealed in a beaker partially filled with DI water at 80 o C (176 o F), broad blisters had formed above and below the waterline on Panel 9-C1. Coating was separating from the substrate in areas. Table 9.A below summarizes the results of the evaluation. TABLE Ex.9.A: Condition After 100 Hrs. in Hot Water The coating on Panel 9 was unchanged after 100 hrs. partially immersed and sealed in hot DI water. No material had leached from the surface. No chalky white deposits were seen on the panel or in the water in the beaker. The coating on one side of Panel 9 was cut through so the steel substrate was exposed and then returned to the hot water test. At the end of another 100 hr. there was no change in the condition of the coating apart from red rust in the scribe. The coating system remained tightly bonded along the scribe. The corrosion-resistance of each of the panels was evaluated also. An "X" was scribed through the coating layer on one side of the large CS panels, Panels 9 and 9-C1, so that the substrate was exposed in the scratch. The scribed panels were placed in a 5% neutral salt fog cabinet per ASTM B-117. The results of the evaluation are reported in Table 9.B below. TABLE Ex.9.B: Condition of Scribed Panels After 5% Salt Fog The coating system on Panels 9-C1 was almost entirely consumed after 1000 hours in salt fog. Heavy white corrosion due to sacrificial corrosion of aluminum in the basecoat was mixed with significant red rust of the steel substrate. In contrast, there was no red rust and little white corrosion on Panels 9 through 2000 hours in salt fog.
Next Patent: BAMA-BINDING AGENTS AND METHODS OF USE THEREOF