The performances of blank sample and chrome-free chemical conversion coating on Mg-based alloys with or without sealing treatment were studied.

Considering the environ-ment protection, chrome-free conversion had become a promising perspective pretreatment.

The corrosion resistance of coatings formed by micro-arc oxidation and free-Cr chemical oxidation on the die casting magnesium alloy surface was compared by immersion tests and electrochemical tests.

Abstract Zinc-Chromium chemical conversion film, called Dacromet in foreign country, has high corrosion resistance as well as no hydrogen brittle, no pollution, high temperature resistance, good combination with steel base and the organic coat, uniformity, and etc.