Non-toxic corrosion-protection conversion coats based on rare earth elements

• US 7,407,711 B2
• Filed: 07/23/2003
• Issued: 08/05/2008
• Est. Priority Date: 01/04/2002
• Status: Expired due to Term

• Current Assignee: University of Dayton
• Original Assignee: University of Dayton
• Inventors: Phelps, Andrew Wells, Sturgill, Jeffrey Allen, Swartzbaugh, Joseph Thomas
• Primary Examiner(s): King; Roy
• Assistant Examiner(s): Zheng; Lois L.
• Application Number:
  US10/625,915
• Publication Number:
  US 20040020568A1
• Time in Patent Office: 1,840 Days
• Field of Search: 148247-248, 148/257, 148274-275, 148/253, 148/285, 147/253, 106/14.05, 106/14.11, 106/14.12, 106/14.41, 106/480, 252/387, 252/389.2, 252/389.4, 428/432, 428/469, 428/457
• US Class Current: 428/469
• CPC Class Codes: C23C 22/34 containing fluorides or complex fluorides
• CPC Class Codes: C23C 22/56 Treatment of aluminium or alloys based thereon
• CPC Class Codes: C23C 22/68 using aqueous solutions with pH between 6 and 8
• CPC Class Codes: Y10T 428/31656 With metal layer
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

Conversion coatings comprising a rare earth element and a valence stabilizer combined to form a rare earth/valence stabilizer complex are described for substrate metals. The rare earth element is selected from cerium, praseodymium, terbium, or combinations thereof, and at least one rare earth element is in the tetravalent oxidation state. The coating bath may also contain a preparative or solubility control agent. The oxidized cerium, praseodymium or terbium is present in the coating in a “sparingly soluble” form. The valence stabilizers can be either inorganic or organic in nature. A number of cerium, praseodymium, or terbium/valence stabilizer combinations are presented that can equal the performance of conventional hexavalent chromium systems.

Claims

1. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and an inorganic valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state in the rare earth/valence stabilizer complex in the solid corrosion-inhibiting conversion coating.

2. The conversion coating of claim 1 wherein the rare earth/valence stabilizer complex has a solubility in water of between about 5×

10<sup>−

1</sup> and about 1×

10<sup>−

5</sup> moles per liter of cerium, praseodymium, or terbium at about 25°

C. and about 760 Torr.

3. The conversion coating of claim 2 wherein the solubility of the rare earth/valence stabilizer complex in water is between about 5×

10<sup>−

2</sup> and about 5×

10<sup>−

5</sup> moles per liter of cerium, praseodymium, or terbium at about 25°

C. and about 760 Torr.

4. The conversion coating of claim 1 wherein there is an electrostatic barrier layer around the rare earth/valence stabilizer complex in aqueous solution.

5. The conversion coating of claim 1 wherein the rare earth/valence stabilizer complex acts as an ion exchange agent towards corrosive ions.

6. The conversion coating of claim 1 wherein the conversion coating is between about 25 and about 10,000 nanometers thick.

7. The conversion coating of claim 6 wherein the conversion coating is between about 100 and about 500 nanometers thick.

8. The conversion coating of claim 1 wherein the conversion coating has a morphology which enhances adhesion of a coating applied over the conversion coating.

9. The conversion coating of claim 1 wherein the rare earth/valence stabilizer complex has a central cavity containing a cerium, praseodymium, or terbium ion and an additional ion.

10. The conversion coating of claim 9 wherein the additional ion is B⁺³, Al⁺³, Si⁺⁴, P⁺⁵, Ti⁺⁴, V⁺⁵, V⁺⁴, Cr⁺⁶, Cr⁺³, Mn⁺⁴, Mn⁺³, Mn⁺², Fe⁺³, Fe⁺², Co⁺², Co⁺³, Ni⁺² , Ni⁺³, Ni⁺⁴, Cu⁺², Cu⁺³, Zn⁺², Ga⁺³, Ge⁺⁴, As⁺⁵, As⁺³, or Zr⁺⁴.

11. The conversion coating of claim 1 wherein the inorganic valence stabilizer is selected from molybdates, tungstates, vanadates, niobates, tantalates, tellurates, periodates, iodates, carbonates, antimonates, stannates, phosphates, nitrates, bromates, sulfates, titanates, zirconates, bismuthates, germanates, arsenates, selenates, borates, aluminates, silicates, or combinations thereof.

12. The conversion coating of claim 11 wherein the valence stabilizer is the inorganic valence stabilizer selected from molybdates, tungstates, vanadates, niobates, tantalates, tellurates, periodates, iodates, carbonates, antimonates, stannates, phosphates, nitrates, bromates, sulfates, or combinations thereof.

13. The conversion coating of claim 1 wherein the rare earth/valence stabilizer complex further comprises a solubility control agent.

14. The conversion coating of claim 13 wherein the solubility control agent is a cationic solubility control agent or an anionic solubility control agent.

15. The conversion coating of claim 14 wherein the solubility control agent is the cationic solubility control agent selected from H⁺;

Li⁺;

Na⁺;

K⁺;

Rb⁺;

Cs⁺;

NH₄⁺;

Mg⁺²;

Ca⁺²;

Sr⁺²;

Be⁺²;

Ba⁺²;

Y⁺³;

La⁺³;

Ce⁺³;

Ce⁺⁴;

Nd⁺³;

Pr⁺³;

Sc⁺³;

Sm⁺³;

Eu⁺³;

Eu⁺²;

Gd⁺³;

Tb⁺³;

Dy⁺³;

Ho⁺³;

Er⁺³;

Tm⁺³;

Yb⁺³;

Lu⁺³;

Ti⁺⁴;

Zr⁺⁴;

Ti⁺³;

Hf⁺⁴;

Nb⁺⁵;

Ta⁺⁵;

Nb⁺⁴;

Ta⁺⁴;

V⁺⁵;

V⁺⁴;

V⁺³;

Mo⁺⁶;

W⁺⁶;

Mo⁺⁵;

W⁺⁵;

Mo⁺⁴;

W⁺⁴;

Cr⁺³;

Mn⁺²;

Mn⁺³;

Mn⁺⁴;

Fe⁺²;

Fe⁺³;

Co⁺²;

Co⁺³;

Ni⁺²;

Ni⁺³;

Ni⁺⁴;

Ru⁺²;

Ru⁺³;

Ru⁺⁴;

Rh⁺³;

Ir⁺³;

Rh⁺²;

Ir⁺²;

Pd⁺⁴;

Pt⁺⁴;

Pd⁺²;

Pt⁺²;

Os⁺⁴;

Cu⁺;

Cu⁺²;

Cu⁺³;

Ag⁺;

Ag⁺²;

Ag⁺³;

Au⁺;

Au⁺²;

Au⁺³;

Zn⁺²;

Cd⁺²;

Hg⁺;

Hg⁺²;

Al⁺³;

Ga⁺³;

Ga⁺;

In⁺³;

In⁺;

Tl⁺³;

Tl⁺;

Ge⁺⁴;

Ge⁺²;

Sn⁺⁴;

Sn⁺²;

Pb⁺⁴;

Pb⁺²;

Sb⁺³;

Sb⁺⁵;

As⁺³;

As⁺⁵;

Bi⁺³;

Bi⁺⁵;

organic compounds containing at least one N⁺ site;

organic compounds containing at least one phosphonium site;

organic compounds containing at least one arsonium site;

organic compounds containing at least one stibonium site;

organic compounds containing at least one oxonium site;

organic compounds containing at least one sulfonium site;

organic compounds containing at least one selenonium site;

organic compounds containing at least one iodonium site;

quaternary ammonium compounds having a formula NR₄⁺, where R is an alkyl, aromatic, or acyclic organic constituent;

or combinations thereof.

16. The conversion coating of claim 15 wherein the cationic solubility control agent is selected from H⁺;

Li⁺;

Na⁺;

K⁺;

Rb⁺;

Cs⁺;

NH₄⁺;

Mg⁺²;

Ca⁺²;

Sr⁺²;

Y⁺³;

La⁺³;

Ce⁺³;

Nd⁺³;

Pr⁺³;

Sc⁺³;

Sm⁺³;

Eu⁺³;

Eu⁺²;

Gd⁺³;

Tb⁺³;

Dy⁺³;

Ho⁺³;

Er⁺³;

Tm⁺³;

Yb⁺³;

Lu⁺³;

Ti⁺⁴;

Zr⁺⁴;

Ti⁺³;

Hf⁺⁴;

Nb⁺⁵;

Ta⁺⁵;

Nb⁺⁴;

Ta⁺⁴;

Mo⁺⁶;

W⁺⁶;

Mo⁺⁵;

W⁺⁵;

Mo⁺⁴;

W⁺⁴;

Mn⁺²;

Mn⁺³;

Mn⁺⁴;

Fe⁺²;

Fe⁺³;

Co⁺²;

Co⁺³;

Ru⁺²;

Ru⁺³;

R⁺⁴;

Rh⁺³;

Ir⁺³;

Rh⁺²;

Ir⁺²;

Pd⁺⁴;

Pt⁺⁴;

Pd⁺²;

Pt⁺²;

Cu⁺;

Cu⁺²;

Cu⁺³;

Ag⁺;

Ag⁺²;

Ag⁺³;

Au⁺;

Au⁺²;

Au⁺³;

Zn⁺²;

Al⁺³;

Ga⁺³;

Ga⁺;

In⁺³;

In⁺;

Ge⁺⁴;

Ge⁺²;

Sn⁺⁴;

Sn⁺²;

Sb⁺³;

Sb⁺⁵;

Bi⁺³;

Bi⁺⁵;

organic compounds containing at least one N⁺ site;

organic compounds containing at least one phosphonium site;

organic compounds containing at least one stibonium site;

organic compounds containing at least one oxonium site;

organic compounds containing at least one sulfonium site;

organic compounds containing at least one iodonium site;

quaternary ammonium compounds having a formula NR₄⁺, where R is an alkyl, aromatic, or acyclic organic constituent;

or combinations thereof.

17. The conversion coating of claim 14 wherein the solubility control agent is the anionic solubility control agent selected from fluorotitanates, chlorotitanates, fluorozirconates, chlorozirconates, fluoroniobates, chloroniobates, fluorotantalates, chiorotantalates, molybdates, tungstates, permanganates, fluoromanganates, chloromanganates, fluoroferrates, chloroferrates, fluorocobaltates, chlorocobaltates, fluorozincates, chlorozincates, borates, fluoroborates, fluoroaluminates, chioroaluminates, carbonates, silicates, fluorosilicates, fluorostannates, nitrates, nitrites, azides, cyanamides, phosphates, phosphites, phosphonates, phosphinites, thiophosphates, thiophosphites, thiophosphonates, thiophosphinites, fluorophosphates, fluoroantimonates, chloroantimonates, sulfates, sulfites, sulfonates, thiosulfates, dithionites, dithionates, fluorosulfates, tellurates, fluorides, chlorides, chiorates, perchlorates, bromides, bromates, iodides, iodates, periodates, heteropolyanions, ferricyanides, ferrocyanides, cyanocobaltates, cyanocuprates, cyanomanganates, cyanates, cyanatoferrates, cyanatocobaltates, cyanatocuprates, cyanatomanganates, thiocyanates, thiocyanatoferrates, thiocyanatocobaltates, thiocyanatocuprates, thiocyanatomanganates, cyanamides, cyanamidoferrates, cyanamidocobaltates, cyanamidocuprates, cyanamidomanganates, nitritoferrates, nitritocobaltates, azides, (thio)carboxylates, di(thio)carboxylates, tri(thio)carboxylates, tetra(thio)carboxylates, (thio)phenolates, di(thio)phenolates, tri(thio)phenolates, tetra(thio)phenolates, (thio)phosphonates, di(thio)phosphonates, tri(thio)phosphonates, (thio)phosphonamides, di(thio)phosphonamides, tri(thio)phosphonamides, amino(thio)phosphonates, diamino(thio)phosphonates, triamino(thio)phosphonates, imino(thio)phosphonates, diimino(thio)phosphonates, (thio)sulfonates, di(thio)sulfonates, tri(thio)sulfonates, (thio)sulfonamides, di(thio)sulfonamides, tri(thio)sulfonamides, amino(thio)sulfonates, diamino(thio)sulfonates, triamino(thio)sulfonates, imino(thio)sulfonates, diimino(thio)sulfonates, (thio)borates, di(thio)borates, (thio)boronates, organic silicates, stibonates, cyanides, cyanoebromates, cyanonickelates, cyanatochromates, cyanatonickelates, thiocyanatochromates, thiocyanatonickelates, cyanamidochromates, cyanamidonickelates, nitritonickelates, arsonates, diarsonates, triarsonates, organic selenates, diselenates, triselenates, arsenates, arsenites, fluoroarsenates, chioroarsenates, selenates, selenites, fluorothallates, chiorothallates, iodomercury anions, chioromercurates, bromomercurates, osmates, fluoronickelates, chromates, Reinecke'"'"'s salt, vanadates, or combinations thereof.

18. The conversion coating of claim 17 wherein the anionic solubility control agent is selected from fluorotitanates, chiorotitanates, fluorozirconates, chiorozirconates, fluoroniobates, chloroniobates, fluorotantalates, chlorotantalates, molybdates, tungstates, permanganates, fluoromanganates, chioromanganates, fluoroferrates, chloroferrates, fluorocobaltates, chlorocobaltates, fluorozincates, chlorozincates, borates, fluoroborates, fluoroaluminates, chloroaluminates, carbonates, silicates, fluorosilicates, fluorostannates, nitrates, nitrites, azides, cyanamides, phosphates, phosphites, phosphonates, phosphinites, thiophosphates, thiophosphites, thiophosphonates, thiophosphinites, fluorophosphates, fluoroantimonates, chloroantimonates, sulfates, sulfites, sulfonates, thiosulfates, dithionites, dithionates, fluorosulfates, tellurates, fluorides, chlorides, chlorates, perchiorates, bromides, bromates, iodides, iodates, periodates, heteropolyanions, ferricyanides, ferrocyanides, cyanocobaltates, cyanocuprates, cyanomanganates, cyanates, cyanatoferrates, cyanatocobaltates, cyanatocuprates, cyanatomanganates, thiocyanates, thiocyanatoferrates, thiocyanatocobaltates, thiocyanatocuprates, thiocyanatomanganates, cyanamides, cyanamidoferrates, cyanamidocobaltates, cyanamidocuprates, cyanamidomanganates, nitritoferrates, nitritocobaltates, azides, (thio)carboxylates, di(thio)carboxylates, tri(thio)carboxylates, tetra(thio)carboxylates, (thio)phenolates, di(thio)phenolates, tri(thio)phenolates, tetra(thio)phenolates, (thio)phosphonates, di(thio)phosphonates, tri(thio)phosphonates, (thio)phosphonamides, di(thio)phosphonamides, tri(thio)phosphonamides, amino(thio)phosphonates, diamino(thio)phosphonates, triamino(thio)phosphonates, imino(thio)phosphonates, diimino(thio)phosphonates, (thio)sulfonates, di(thio)sulfonates, tri(thio)sulfonates, (thio)sulfonamides, di(thio)sulfonamides, tri(thio)sulfonamides, amino(thio)sulfonates, diamino(thio)sulfonates, triamino(thio)sulfonates, imino(thio)sulfonates, diimino(thio)sulfonates, (thio)borates, di(thio)borates, (thio)boronates, organic silicates, stibonates, or combinations thereof.

19. The conversion coating of claim 1 wherein the conversion coating is colored.

20. The conversion coating of claim 19 further comprising an agent which improves color-fastness of the conversion coating.

21. The conversion coating of claim 20 wherein the agent which improves color-fastness is selected from an active UV blocker, a passive UV blocker, a brightener, or a combination thereof.

22. The conversion coating of claim 21 wherein the agent which improves color-fastness is the active UV blocker selected from carbon black, graphite, phthalocyanines, or combinations thereof.

23. The conversion coating of claim 21 wherein the agent which improves color-fastness is the passive UV blocker selected from titanium oxide, tin oxide, lead oxide, silicon oxide, silicates, aluminosilicates, or combinations thereof.

24. The conversion coating of claim 21 wherein the agent which improves color-fastness is the brightener selected from sulfonic acids, sulfonates, sulfonamides, sulfinic acids, sulfinates, sulfones, cyanides, nonionic surfactants, or combinations thereof.

25. The conversion coating of claim 19 wherein the color is formed by a dye selected from vat dyes, mordant dyes, lake dyes, disperse dyes, azo dyes, triazene dyes, triphenylmethane dyes, azine dyes, formazan dyes, phthalocyanine dyes, Schiff Base dyes, naturally-occurring dyes, inorganic pigments, or combinations thereof.

26. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and an inorganic valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein

the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof,

at least one rare earth element is in the tetravalent oxidation state in the rare earth/valence stabilizer complex in the solid corrosion-inhibiting conversion coating, and

the rare earth/valence stabilizer complex is sparingly soluble in water at about 25°

C. and about 760 Torr.

27. A solid corrosion-inhibiting conversion coating formed on a substrate metal, the conversion coating comprising a rare earth element and a valence stabilizer combined to form a rare earth/valence stabilizer complex within the solid corrosion-inhibiting conversion coating, wherein the rare earth element is selected from cerium, praseodymium, terbium, or a combination thereof, and at least one rare earth element is in the tetravalent oxidation state, wherein the rare earth/valence stabilizer complex has a central cavity containing a cerium, praseodymium, or terbium ion and an additional ion, wherein the additional ion is B⁺³, Al⁺³, Si⁺⁴, P⁺⁵, Ti⁺⁴, V⁺⁵, V⁺⁴, Cr⁺⁶, Cr⁺³, Mn⁺⁴, Mn⁺³, Mn⁺², Fe⁺³, Fe⁺², Co⁺², Co⁺³, Ni⁺² , Ni⁺³, Ni⁺⁴, Cu⁺², Cu⁺³, Zn⁺², Ga⁺³, Ge⁺⁴, As⁺⁵, As⁺³, or Zr⁺⁴.

28. The conversion coating of claim 27 wherein the rare earth/valence stabilizer complex has a solubility in water of between about 5×

10<sup>−

1</sup> and about 1×

10<sup>−

5</sup> moles per liter of cerium, praseodymium, or terbium at about 25°

C. and about 760 Torr.

29. The conversion coating of claim 28 wherein the solubility of the rare earth/valence stabilizer complex in water is between about 5×

10<sup>−

2</sup> and about 5×

10<sup>−

5</sup> moles per liter of cerium, praseodymium, or terbium at about 25°

C. and about 760 Torr.

30. The conversion coating of claim 27 wherein there is an electrostatic barrier layer around the rare earth/valence stabilizer complex in aqueous solution.

31. The conversion coating of claim 27 wherein the rare earth/valence stabilizer complex acts as an ion exchange agent towards corrosive ions.

32. The conversion coating of claim 27 wherein the conversion coating is between about 25 and about 10,000 nanometers thick.

33. The conversion coating of claim 32 wherein the conversion coating is between about 100 and about 500 nanometers thick.

34. The conversion coating of claim 27 wherein the conversion coating has a morphology which enhances adhesion of a coating applied over the conversion coating.

35. The conversion coating of claim 27 wherein the valence stabilizer is an inorganic valence stabilizer selected from molybdates, tungstates, vanadates, niobates, tantalates, tellurates, periodates, iodates, carbonates, antimonates, stannates, phosphates, nitrates, bromates, sulfates, titanates, zirconates, bismuthates, germanates, arsenates, selenates, borates, aluminates, silicates, or combinations thereof.

36. The conversion coating of claim 35 wherein the valence stabilizer is the inorganic valence stabilizer selected from molybdates, tungstates, vanadates, niobates, tantalates, tellurates, periodates, iodates, carbonates, antimonates, stannates, phosphates, nitrates, bromates, sulfates, or combinations thereof.

37. The conversion coating of claim 27 wherein the rare earth/valence stabilizer complex further comprises a solubility control agent.

38. The conversion coating of claim 37 wherein the solubility control agent is a cationic solubility control agent or an anionic solubility control agent.

39. The conversion coating of claim 38 wherein the solubility control agent is the cationic solubility control agent selected from H⁺;

Li⁺;

Na⁺;

K⁺;

Rb⁺;

Cs⁺;

NH₄⁺;

Mg⁺²;

Ca⁺²;

Sr⁺²;

Be⁺²;

Ba⁺²;

Y⁺³;

La⁺³;

Ce⁺³;

Ce⁺⁴;

Nd⁺³;

Pr⁺³;

Sc⁺³;

Sm⁺³;

Eu⁺³;

Eu⁺²;

Gd⁺³;

Tb⁺³;

Dy⁺³;

Ho⁺³;

Er⁺³;

Tm⁺³;

Yb⁺³;

Lu⁺³;

Ti⁺⁴;

Zr⁺⁴;

Ti⁺³;

Hf⁺⁴;

Nb⁺⁵;

Ta⁺⁵;

Nb⁺⁴;

Ta⁺⁴;

V⁺⁵;

V⁺⁴;

V⁺³;

Mo⁺⁶;

W⁺⁶;

Mo⁺⁵;

W⁺⁵;

Mo⁺⁴;

W⁺⁴;

Cr⁺³;

Mn⁺²;

Mn⁺³;

Mn⁺⁴;

Fe⁺²;

Fe⁺³;

Co⁺²;

Co⁺³;

Ni⁺²;

Ni⁺³;

Ni⁺⁴;

Ru⁺²;

Ru⁺³;

Ru⁺⁴;

Rh⁺³;

Ir⁺³;

Rh⁺²;

Ir⁺²;

Pd⁺⁴;

Pt⁺⁴;

Pd⁺²;

Pt⁺²;

Os⁺⁴;

Cu⁺;

Cu⁺²;

Cu⁺³;

Ag⁺;

Ag⁺²;

Ag⁺³;

Au⁺;

Au⁺²;

Au⁺³;

Zn⁺²;

Cd⁺²;

Hg⁺;

Hg⁺²;

Al⁺³;

Ga⁺³;

Ga⁺;

In⁺³;

In⁺;

Tl⁺³;

Tl⁺;

Ge⁺⁴;

Ge⁺²;

Sn⁺⁴;

Sn⁺²;

Pb⁺⁴;

Pb⁺²;

Sb⁺³;

Sb⁺⁵;

As⁺³;

As⁺⁵;

Bi⁺³;

Bi⁺⁵;

organic compounds containing at least one N⁺ site;

organic compounds containing at least one phosphonium site;

organic compounds containing at least one arsonium site;

organic compounds containing at least one stibonium site;

organic compounds containing at least one oxonium site;

organic compounds containing at least one sulfonium site;

organic compounds containing at least one selenonium site;

organic compounds containing at least one iodonium site;

quaternary ammonium compounds having a formula NR₄⁺, where R is an alkyl, aromatic, or acyclic organic constituent;

or combinations thereof.

40. The conversion coating of claim 39 wherein the cationic solubility control agent is selected from H⁺;

Li⁺;

Na⁺;

K⁺;

Rb⁺;

Cs⁺;

NH₄⁺;

Mg⁺²;

Ca⁺²;

Sr⁺²;

Y⁺³;

La⁺³;

Ce⁺³;

Nd⁺³;

Pr⁺³;

Sc⁺³;

Sm⁺³;

Eu⁺³;

Eu⁺²;

Gd⁺³;

Tb⁺³;

Dy⁺³;

Ho⁺³;

Er⁺³;

Tm⁺³;

Yb⁺³;

Lu⁺³;

Ti⁺⁴;

Zr⁺⁴;

Ti⁺³;

Hf⁺⁴;

Nb⁺⁵;

Ta⁺⁵;

Nb⁺⁴;

Ta⁺⁴;

Mo⁺⁶;

W⁺⁶;

Mo⁺⁵;

W⁺⁵;

Mo⁺⁴;

W⁺⁴;

Mn⁺²;

Mn⁺³;

Mn⁺⁴;

Fe⁺²;

Fe⁺³;

Co⁺²;

Co⁺³;

Ru⁺²;

Ru⁺³;

R⁺⁴;

Rh⁺³;

Ir⁺³;

Rh⁺²;

Ir⁺²;

Pd⁺⁴;

Pt⁺⁴;

Pd⁺²;

Pt⁺²;

Cu⁺;

Cu⁺²;

Cu⁺³;

Ag⁺;

Ag⁺²;

Ag⁺³;

Au⁺;

Au⁺²;

Au⁺³;

Zn⁺²;

Al⁺³;

Ga⁺³;

Ga⁺;

In⁺³;

In⁺;

Ge⁺⁴;

Ge⁺²;

Sn⁺⁴;

Sn⁺²;

Sb⁺³;

Sb⁺⁵;

Bi⁺³;

Bi⁺⁵;

organic compounds containing at least one N⁺ site;

organic compounds containing at least one phosphonium site;

organic compounds containing at least one stibonium site;

organic compounds containing at least one oxonium site;

organic compounds containing at least one sulfonium site;

organic compounds containing at least one iodonium site;

quaternary ammonium compounds having a formula NR₄⁺, where R is an alkyl, aromatic, or acyclic organic constituent;

or combinations thereof.

41. The conversion coating of claim 27 wherein the conversion coating is colored.

42. The conversion coating of claim 41 further comprising an agent which improves color-fastness of the conversion coating.

43. The conversion coating of claim 42 wherein the agent which improves color-fastness is selected from an active UV blocker, a passive UV blocker, a brightener, or a combination thereof.

44. The conversion coating of claim 43 wherein the agent which improves color-fastness is the active UV blocker selected from carbon black, graphite, phthalocyanines, or combinations thereof.