PROCESSES AND COMPOSITIONS FOR IMPROVING CORROSION PERFORMANCE OF ZIRCONIUM OXIDE PRETREATED ZINC SURFACES

摘要

A method of improving corrosion resistance of a metal substrate comprising a zinc surface coated with zirconium oxide conversion coating by, prior to conversion coating, contacting the zinc surface with a composition comprising:
a) iron(III) ions,b) a source of hydroxide ion;c) at least one complexing agent selected from organic compounds which have at least one functional group —COOX, wherein X represents either a H or an alkali and/or alkaline earth metal;d) 0.0 to about 4 g/l cobalt (II) ions; andoptionallye) a source of silicate:wherein the composition has a pH of at least 10.

主权项

1. A method for improving corrosion performance of a metal substrate comprising steps of:)
1. providing a metal substrate comprising at least one zinc or zinc alloy surface; 2. contacting said surface with an alkaline pre-rinse composition comprising:
a) iron(III) ions,b) a source of hydroxide ion;c) at least one complexing agent selected from organic compounds which have at least one functional group —COOX, wherein X represents either a H or an alkali and/or alkaline earth metal;d) 0.0 to about 4 g/l cobalt (II) ions; andoptionallye) a source of silicate:wherein the composition has a pH of at least 10; 3. optionally rinsing said surface; 4. applying to the metal substrate a zirconium-based metal pretreatment coating composition comprising zirconium, thereby forming a pretreatment coating on the metal substrate; and 5.) optionally applying a paint to the metal pretreatment coated metal substrate.