Preparation of robust, self-cleaning and anti-corrosion superhydrophobic Ca-P/chitosan (CS) composite coating on AZ31 magnesium alloy

Magnesium (Mg) and its alloys are promising materials in the industrial and biomedical field, but the excessive corrosion rate limits their practical application. To improve the anti-corrosion property of Mg alloys, the composite coating composed of calcium phosphate (CaP) and chitosan (CS) was prepared on AZ31 Mg alloy via simple electrophoretic deposition and chemical conversion method. The water contact angle (WCA) of the composite coating was as high as 158.6° after being modified by stearic acid. Furthermore, a superhydrophobic single CaP coating with the WCA value of 158.5° was fabricated by a chemical conversion method and low energy modification. The superhydrophobic coatings exhibited good self-cleaning properties to prevent the pollution of different pollutants. Furthermore, the obtained superhydrophobic Ca-P/CS composite coating can withstand more times of tape-peeling because of its better bonding ability. Moreover, compared with the superhydrophobic single CaP coating, the composite coating can provide more effective protection to the AZ31 substrate in electrochemical measurements and immersion test. Therefore, the superhydrophobic Ca-P/CS composite coating with significant performance advantages can expand the application fields of Mg alloys.