Abstract

New waterborne Al-Zn-Si-RE coatings with improved corrosion resistance were introduced in this study. The corrosion resistance of Al-Zn-Si-RE coatings was evaluated by electrochemical measurements and salt spray test. Evolution of microstructure and phase composition at different exposure time in salt spray test was investigated by scanning electron microscopy and X-ray diffraction technique. The results indicate that Al-Zn-Si-RE coatings provide effective sacrificial protection to the steel substrate but exhibit lower corrosion rate and higher corrosion resistance compared to zinc aluminum coatings. The dense continuous corrosion layer formed on Al-Zn-Si-RE coating acts as a barrier layer, limiting the transport of aggressive species towards the coating-substrate interface and the corrosion rate of the coating; Zinc aluminum hydroxy carbonates are the dominant components in the corrosion layer of Al-Zn-Si-RE coatings.

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