Trivalent chromium-containing composition for aluminum and aluminum alloys
AssigneeHenkel AG & Co. KGaA
InventorsKirk Kramer, Lisa Salet
Life of this patent
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Abstract
A low sludge trivalent chromium based conversion coating bath is provided which forms corrosion resistant coatings on aluminum and aluminum alloys by contact with the bath, which is suitable for use as a rinseable or dry-in place conversion coating for metal, that comprises trivalent chromium cations, fluorometallate anions, guanidinium ions and at least one organic anti-corrosion additive, and other optional components, as well as methods of making and using same, and metals coated using the compositions, the coated aluminum serving as an effective base for paint primers.
Claims21
A composition for coating a metal surface, said composition comprising water and:
- (A) a source of fluorometallate anions, each of said anions consisting of:
- (i) at least four fluorine atoms;
- and
- (ii) at least one atom of an element “M” selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron;
- and, optionally, one or both of
- (iii) at least one ionizable hydrogen atom;
- and
- (iv) at least one oxygen atom;
- (B) a source of chromium(III) cations;
- wherein the molar ratio of chromium(III) cations to component (A) ranges from 20:1 to 50:1;
- (C) a source of guanidinium cation;
- and, optionally, one or more of the following components:
- (D) a source of nitrate anions;
- (E) an organic corrosion inhibitor that is not part of any of immediately previously recited components (A) through (D);
- (F) a component of free fluoride ions that are not part of any of immediately previously recited components (A) through (E);
- (G) a component of surfactant molecules that are not part of any of immediately previously recited components (A) through (F);
- (H) a pH adjusting component that is not part of any of the immediately previously recited components (A) through (G);
- and
- (I) a viscosity increasing component that is not part of any of the immediately previously recited components (A) through (H);
- said composition being substantially free of hexavalent chromium.
A composition for coating a metal surface, said composition comprising water and:
- (A) a source of ions of at least one element “M” selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron;
- (B) a source of chromium(III) cations;
- wherein the molar ratio of chromium(III) cations to element “M” ranges from 20:1 to 50:1;
- (C) a source of guanidinium cation;
- and, optionally, one or more of the following components:
- (D) a source of nitrate anions;
- (E) an organic corrosion inhibitor, that is not part of any of immediately previously recited components (A) through (D);
- (F) a component of free fluoride ions that are not part of any of immediately previously recited components (A) through (E);
- (G) a component of surfactant molecules that are not part of any of immediately previously recited components (A) through (F);
- (H) a pH adjusting component that is not part of any of the immediately previously recited components (A) through (G);
- and
- (I) a viscosity increasing component that is not part of any of the immediately previously recited components (A) through (H).
Dependencies are inferred from the claim text.