Zinc phosphate coating process
AssigneeHenkel Corporation
InventorLinda S. Kramer
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Abstract
The present invention relates to a composition and process for metal finishing involving the formation of zinc phosphate coatings of desired morphology on a ferrous surface. The inclusion of a hydroxylamine agent in the phosphating bath expands the range of zinc concentrations over which the desired coating morphology is obtained. Zinc and aluminum surface can also be coated with this composition and process.
Claims33
A metal finishing process for producing a predominantly nodular and/or columnar crystalline zinc-iron-phosphate coating on a ferrous surface, over a broadened range of zinc and ferrous ion concentration, which comprises:
- contacting the ferrous surface with an aqueous zinc phosphate conversion coating solution having a zinc/phosphate weight ratio not higher than about 0.27, an effective amount of a hydroxylamine agent to produce the crystalline structure, and wherein said solution is substantially free of nitrite and said zinc concentration is from about 0.02 to 0.2 wt. %.
An aqueous zinc/phosphate solution for producing columnar and/or nodular crystalline coatings on a ferrous surface over a broadened range of zinc and ferrous ion concentrations comprising a zinc phosphate solution having a zinc/phosphate ratio not higher than about 0.27, a columnar and/or nodular crystal forming effective amount of a hydroxylamine agent, the solution being substantially free of nitrite and said zinc concentration is from about 0.02 to 0.2 wt. %.
Dependencies are inferred from the claim text.