Patent Application

App. No. 13/568,277

Abstract

Claims (20)

1 . An aqueous conversion coating composition comprising:

a) from 0 g/l to 300 g/l of aluminum ions;

b) hexafluorozirconic acid or salts thereof;

c) at least one pH adjuster;

d) optionally, a surfactant.

2 . The aqueous conversion coating composition according to claim 1 , wherein the conversion coating composition does not contain chromium or sequestering agents for zinc.

3 . The aqueous conversion coating composition according to claim 1 , wherein the pH adjuster comprises ammonium hydroxide.

4 . The aqueous conversion coating composition according to claim 1 wherein the aluminum ions are from a source comprising aluminum hydroxide.

5 . The aqueous conversion coating composition according to claim 1 wherein the concentration of aluminum ions is from 1 g/l to 50 g/l.

6 . A method of treating a steel substrate to form a conversion coating thereon, the method comprising the steps of

a) contacting the steel substrate with a composition comprising:

i) from 0 g/l to 300 g/l of aluminum ions;

ii) hexafluorozirconic acid or its salts;

iii) at least one pH adjuster;

iv) optionally, a surfactant; and

b) thereafter drying the treated steel surface.

7 . The method according to claim 6 , wherein the conversion coating composition does not contain chromium or sequestering agents for zinc.

8 . The method according to claim 6 , wherein the pH adjuster comprises aluminum hydroxide.

9 . The method according to claim 6 , wherein the aluminum ions are from a source comprising aluminum hydroxide.

10 . The method according to claim 6 , wherein the concentration of aluminum ions is from 1 g/l to 50 g/l.

Assignments (8)