Abstract

A polypyrrole/zinc (PPy/Zn) bilayer coating is prepared to significantly improve the corrosion resistance of ZK60 magnesium alloy in 37 °C Hank's solution to meet the requirements for biodegradable metals. The zinc coating composed of dense and uniform flake-like zinc crystals displays good abrasion resistance and adhesion strength, acting as a vital intermediate layer for growing the PPy film doping with tartrate anions (TA−). The prepared PPy/TA films (10, 20 and 28 μm) on the Zn coating are compact and have high stability in Hank's solution. The electrochemical and hydrogen evolution tests for PPy/Zn/ZK60 specimens show that the PPy/TA film's stability determines the protective performance of PPy/Zn coating in a long immersion period. The PPy(20 μm)/Zn coating has the longest protection time (40 ± 4 days), and too thick PPy film (28 μm) damages its structure to accelerate breakage, developing local corrosion quickly on ZK60. The corrosion mechanism involved is discussed.

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