Method for the post-treatment of metal layers
View Patent ↗A process for treating the surface of a metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Mn, Mo, Ag, Au, Pt, Pd, Rh, Pb, Sn, Ni, Zn, in some cases Fe, and alloys of these metals. An anodic potential is applied to the metal surface in an electrolytic circuit comprising the metal surface, a cathode, and an electrolytic solution that is in contact with the metal surface and in electrically conductive communication with the cathode. The electrolytic solution may contain an electrolyte comprising anions of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof. The anion may comprise a polymer having a pendent moiety selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, sulfate, sulfonate, carboxylate and combinations thereof. The potential applied to the circuit is such that the substrate is anodically oxidized and reacts with the anion to form a composition that imparts an enhanced property to the metal surface. Preferably, the pH of the electrolytic solution is less than about 6.0, the potential applied is between about 0.5 and about 20 volts, and the current density is between about 0.01 and 2 amps/dm 2 of the geometric surface area of metal in contact with the electrolytic solution and is controlled such that nascent cations of said constituent metal produced by anodic oxidation of said constituent metal react with said anions at the metal surface without significant formation of any oxide or hydroxide of said constituent metal.
1. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte comprising a compound having a hydrophobic carbon-carbon chain with hydrophilic anionic functional groups and another anion selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts and the current density between about 0.01 and about 2.0 A/dm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that a constituent metal of said substrate is anodically oxidized and reacts with said compound to form a composition at said surface that imparts an enhanced property to said surface;
wherein the current density and voltage are controlled so that said composition is formed at said surface but no detectable increase in the thickness of any layer comprising an oxide or hydroxide of any of said constituent metals occurs during passage of current in said circuit.
2. The process of claim 1 wherein the substrate is a Cr-based coating on a metal body.
3. The process as set forth in claim 1 wherein the concentration of said another anion in the electrolytic solution is between about 1 and about 50 g/L.
4. The process as set forth in claim 3 wherein the concentration of said another anion in the electrolytic solution is between about 1 and 25 g/L.
5. The process as set forth in claim 1 wherein the conductivity of the electrolytic solution is between about 1 and about 500 millisiemens.
6. The process as set forth in claim 1 wherein passage of current in said electrolytic circuit is terminated when the total electric charge transferred during formation of said composition at said surface is between about 0.05 and about 100 mAhr per dm 2 of the geometric area of said metal surface in contact with said electrolytic solution.
7. The process as set forth in claim 1 wherein no detectable oxide or hydroxide of any of said constituent metals remains at said surface at the time passage of current in said circuit is terminated.
8. The process as set forth in claim 1 wherein the current density is such that nascent cations produced by anodic oxidation of said constituent metal react with said anions at the metal surface without significant formation of any oxide or hydroxide of the constituent metal.
9. The process as set forth in claim 1 wherein a nanolayer comprising said composition is formed at the surface of said metal substrate.
10. The process as set forth in claim 9 wherein the thickness of said nanolayer is not greater than about 100 nm.
11. The process as set forth in claim 9 wherein anodic oxidation causes a loss of a marginal substratum of metal at the surface of said substrate, the thickness of said substratum being at least equal in thickness to said nanolayer.
12. The process as set forth in claim 11 wherein the thickness of said marginal substratum of lost metal exceeds the thickness of said nanolayer, and the thickness of the marginal substratum of lost metal is between about 0.0005 and about 0.5 μm.
13. The process as set forth in claim 1 wherein said compound having a hydrophobic carbon-carbon chain with hydrophilic anionic functional groups comprises a polymer having a pendent moiety selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, sulfate, sulfonate, carboxylate, and combinations thereof.
14. The process as set forth in claim 13 wherein the polymer comprises repeating units derived from vinyl phosphonic or vinyl phosphinic acid.
15. The process as set forth in claim 14 with the polymer comprising a copolymer of (meth)acrylic acid and vinyl phosphonic acid.
16. The process as set forth in claim 1 wherein said metal substrate is substantially free of Al.
17. The process as set forth in claim 1 any of claims 1 through 16 wherein the pH of said aqueous electrolytic solution is not greater than about 6.0.
18. The process as set forth in claim 17 wherein the pH is between about 2.0 and about 5.0.
19. The process as set forth in claim 1 wherein said enhanced property comprises enhanced corrosion resistance.
20. The process as set forth in claim 1 wherein said metal substrate comprises a metal layer on an underlying object or an outer stratum of a metal object.
21. The process of claim 1 wherein said controlling comprises controlling the current density at said surface such that nascent cations of said constituent metal produced by anodic oxidation of said constituent metal react with said compound having a hydrophobic carbon-carbon chain with hydrophilic anionic groups at the metal surface without significant formation of any oxide or hydroxide of said constituent metal.
22. The process as set forth in claim 13 wherein the polymer is substantially entirely dissolved in said aqueous electrolytic solution.
23. A process as set forth in claim 1 wherein said constituent metal comprises Cr.
24. A process as set forth in claim 1 wherein said constituent metal comprises Cu.
25. A process as set forth in claim 1 wherein said constituent metal comprises Ni.
26. A process as set forth in claim 1 wherein said constituent metal comprises Sn.
27. A process as set forth in claim 1 wherein said aqueous electrolytic solution further comprises an aromatic compound having at least one hydroxy group and which comprises a further functional group having a positive inductive effect on the hydroxyl group.
28. A process as set forth in claim 1 wherein said aqueous electrolytic solution further comprises and aromatic compound corresponding to the formula:
wherein R1 is H or OH; R2 is H, OH, F, Cl, Br, —O—R, R—OH, R—COOH, R—CHO, R—O—R, R—CO—R, —SH, —NO 2 , —CN, —COO—R; and R3 to R5 are independently from each other H, C n H 2n+1 , OH, F, Cl, Br, —O—R, R—OH, R—COOH, R—CHO, R—O—R, R—CO—R, —SH, —NO 2 , —CN, —COO—R, wherein R is an unsubstituted or substituted alkyl-group having 1 to 10 carbon.
29. A process as set forth in claim 28 wherein said aromatic compound is selected from the group consisting of phenol, 3-ethoxyphenol, 3,5-dimethoxyphenol, 3-nitrophenol, resorcinol, 4-ethylresorcinol, 4-chlorresorcinol, phloroglucine, pyrogallol, gallic acid, catechol, dihydroxybenzaldehyde, dihydroxytoluene, 3-hydroxyphenylacetic acid, 3-hydroxybezoic acid, n-octyl gallat, guajacol and 3,5,7-trihydroxyflavone.
30. A process as set forth in claim 28 wherein said aromatic compound has a further functional group in the meta-position to a hydroxy group.
31. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte comprising a compound having a hydrophobic carbon-carbon chain with hydrophilic anionic functional groups and another anion selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts to cause anodic oxidation at said metal surface; and
controlling the current density at said surface between about 0.01 and about 2.0 A/dm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that nascent cations of said constituent metal produced by anodic oxidation of said constituent metal react with said compound at the metal surface to form a composition at said metal surface without significant formation of any oxide or hydroxide of said constituent metal.
32. The process as set forth in claim 31 wherein the conductivity of the electrolytic solution is between about 1 and about 500 millisiemens.
33. The process as set forth in claim 32 wherein the conductivity of the electrolytic solution is between about 50 and about 350 millisiemens.
34. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte comprising a compound having a hydrophobic carbon-carbon chain with hydrophilic anionic functional groups and another anion selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts and the current density between about 0.01 and about 2.0 Aldm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that a constituent metal of said substrate is anodically oxidized and reacts with said compound to form at said surface a nanolayer comprising a composition that imparts an enhanced property to said surface;
wherein the current density and voltage are controlled so that said composition is formed at said surface but no detectable increase in the thickness of any layer comprising an oxide or hydroxide of any of said constituent metals occurs during passage of current in said circuit.
35. The process as set forth in claim 34 wherein the thickness of said nanolayer is not greater than about 100 nm.
36. The process as set forth in claim 34 wherein anodic oxidation causes a loss of a marginal substratum of metal at the surface of said substrate, the thickness of said substratum being at least equal in thickness to said nanolayer.
37. The process as set forth in claim 36 wherein the thickness of said marginal substratum of lost metal exceeds the thickness of said nanolayer, and the thickness of the marginal substratum of lost metal is between about 0.0005 and about 0.5 μm.
38. A process as set forth in claim 34 wherein said constituent metal comprises Cr.
39. A process as set forth in claim 34 wherein said constituent metal comprises Cu.
40. A process as set forth in claim 34 wherein said constituent metal comprises Ni.
41. A process as set forth in claim 34 wherein said constituent metal comprises Sn.
42. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte comprising a compound having a hydrophobic carbon-carbon chain with hydrophilic anionic functional groups and another anion selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts and the current density between about 0.01 and about 2.0 A/dm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that a constituent metal of said substrate is anodically oxidized and reacts with said compound to form a composition at said surface that imparts an enhanced property to said surface, passage of current in said electrolytic circuit being terminated when the total electric charge transferred during formation of said composition at said surface is between about 0.05 and about 100 mAhr per dm 2 of the geometric area of said metal surface in contact with said electrolytic solution;
wherein the current density and voltage are controlled so that said composition is formed at said surface but no detectable increase in the thickness of any layer comprising an oxide or hydroxide of any of said constituent metals occurs during passage of current in said circuit.
43. A process as set forth in claim 42 wherein wherein the conductivity of the electrolytic solution is between about 1 and about 500 millisiemens.
44. The process as set forth in claim 43 wherein the conductivity of the electrolytic solution is between about 50 and about 350 millisiemens.
45. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte comprising a polymer comprising repeat units selected from the group consisting of vinyl phosphate and vinyl and phosphinate; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts and the current density between about 0.01 and about 2.0 Aldm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that a constituent metal of said substrate is anodically oxidized and reacts with said compound to form a composition at said surface that imparts an enhanced property to said surface;
wherein current density and voltage are controlled so that said composition is formed at said surface but no detectable increase in the thickness of any layer comprising an oxide or hydroxide of any of said constituent metals occurs during passage of current in said circuit.
46. A method as set forth in claim 45 wherein the polymer comprises repeating units derived from vinyl phosphonic or vinyl phosphinic acid.
47. The process as set forth in claim 46 comprising a copolymer of (meth)acrylic acid and vinyl phosphonic acid.
48. A process for treating the surface of a non-ferrous metal substrate comprising a constituent metal selected from the group consisting of Cr, Cu, Sn, Ni, and alloys thereof, the method comprising:
applying an anodic potential to said metal surface in an electrolytic circuit comprising said metal surface, a cathode, and an aqueous electrolytic solution in contact with said metal surface and in electrically conductive communication with said cathode, said electrolytic solution containing an electrolyte containing between about 1 and about 50 g/L of an anion comprising a polymer having a pendent moiety selected from the group consisting of phosphate, phosphonate, phosphite, phosphinate, nitrate, borate, silicate, molybdate, tungstate, carboxylate, oxalate and combinations thereof; and
controlling the potential applied to said circuit between about 0.5 and about 3.0 volts and the current density between about 0.01 and about 2.0 Aldm 2 of the geometric area of said metal surface in contact with said electrolytic solution such that a constituent metal of said substrate is anodically oxidized and reacts with said compound to form a composition at said surface that imparts an enhanced property to said surface;
wherein the current density and voltage are controlled so that said composition is formed at said surface but no detectable increase in the thickness of any layer comprising an oxide or hydroxide of any of said constituent metals occurs during passage of current in said circuit.
49. A method as set forth in claim 48 wherein the concentration of said another anion in the electrolytic solution is between about 1 and 25 g/L.
50. A process as set forth in claim 49 wherein the conductivity of the electrolytic solution is between about 50 and about 350 millisiemens.