Rinsable metal pretreatment methods and compositions
View Patent ↗Chromate-free and metal phosphate free treatments and compositions for applying a conversion or passivation coating for metals, more particularly, steel, zinc coated steel, and aluminum surfaces. The methods of the invention comprise contacting the requisite metal surface with a treatment composition comprising a member or members comprising one or more Group IV B elements, fluoride, and phosphonic acid or phosphonate. Optionally, a silane may be added as a treatment component.
1. A method of coating a metal or metal alloy surface comprising contacting said surface with an effective amount of a chromate free aqueous treatment solution or dispersion comprising (a) a material or materials comprising one or more elements selected from Group IV B elements, (b) fluoride, (c) a mixed solution of linear EBO and cyclic EBO.
2. A method as recited in claim 1 wherein (a) comprises H 2 ZrF 6 and H 2 TiF 6 .
3. A method as recited in claim 1 further comprising at least one more phosphonic acid or phosphonate.
4. A method as recited in claim 3 , wherein said at least one more phosphonic acid or phosphonate (c) is selected from the group consisting of the formulas II, Ill, or IV, wherein formula II has the structure:
wherein R 1 is PO 3 X 2 or R 2 PO 3 X 2 wherein X 2 is a cation or H; R 2 is C 1 -C 5 alkylene and Z is a member selected from H, halo, C 1 -C 5 alkyl, NO 2 and COOH; formula III has the structure:
wherein X is independently chosen from a cation or H; and R 3 is C 1 -C 5 alkyl, C 1 -C 5 carboxyalkyl, C 1 -C 5 5 phosphonoalkyl, C 1 -C 5 siloxyalkyl, and C 1 -C 5 iminoalkyl or C 1 -C 5 phosphonoimino alkyl; and
wherein X is as defined above; R 4 and R 5 are independently chosen from H, C 1 -C 5 alkyl, C 1 -C 5 hydroxyalkyl, C 1 -C 5 phosphonoalkyl, with the proviso that R 4 and R 5 may, together as covalently linked, form a cyclic structure; R 6 may or may not be present, and when present is a C 1 -C 5 alkylene moiety; and Q is N or N oxide + .
5. A method as recited in claim 4 wherein said at least one more phosphonic acid or phosphonate (c) has the formula IV.
6. A method as recited in claim 4 wherein said at least one more phosphonic acid or phosphonate (c) has the formula (II).
7. A method as recited in claim 6 wherein said at least one more phosphonic acid and/or phosphonate (c) is a member or members selected from the group consisting of
4-bromobenzylphosphonic acid,
4-tertbutylbenzylphosphonic acid,
phenylphosphonic acid,
4-hydroxybenzylphosphonic acid,
4-nitrobenzylphosphonic acid,
4-methylbenzylphosphonic acid,
4-carboxybenzylphosphonic acid and
4-bromobenzyl phosphonate ethyl ester.
8. A method as recited in claim 4 wherein said at least one more phosphonic acid or phosphonate (c) has the formula III.
9. A method as recited in claim 8 wherein said at least one more phosphonic and/or phosphonate (c) is a member or members selected from the group consisting of
2-carboxyethylphosphonic acid,
trihydroxysilylpropyl phosphonate;
1,2,-diethylenediphosphonic acid,
iminobis(methylphosphonic acid) and
tertbutylphosphonic acid.
10. A method as recited in claim 1 further comprising at least one silane.
11. A method as recited in claim 10 wherein said at least on silane is selected from the group of alkoxysilane, aminosilane, ureidosilane, glycidoxysilane or mixtures thereof.