What is Conversion Treatment?

This is a surface treatment method by which non-metal coatings such as oxidative products, phosphate, sulfide, etc. are chemically formed to cover base metal to obtain corrosion resistance and appearance improving of base metals and adhesion as painted base.

By method, anodic oxidation as electrochemical method, and chromate treatment, phosphate treatment, chemical coloring as chemical method are taken.

Conversion Treatment for Zn Plated Surface

Zn plated surface is not usually used as it is since the surface with Zn, a poor metal, produces white rust, which is corrosion products, degrading the appearance soon due to wetting and contamination in the surrounding atmosphere.

Mostly, trivalent conversion treatment as post treatment is applied on the surface in response to each purpose. This treatment improves not only its corrosion resistance significantly but also its appearance and properties. At present, by appearance, silver or black color is used.

Trivalent Chromium Conversion Treatment

*Activation
5-second dipping in 0.2-1% nitric acid removes brightening agent for plating as well as activates the surface for normal treatment

*Trivalent Chromium Conversion Treatment
Through chemical reaction caused by dipping the materials in the acidic solution composed of trivalent chromium salt basically coatings mainly structured by chromium oxide or chromium hydroxide form on the surface.

*Finishing Treatment
This is applied, if required, to improve properties such as corrosion resistance, appearance, stabilization of friction coefficient. (It may be skipped.)

Trivalent Chromium Conversion Coating Structure and Corrosion Resistance Mechanism

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