Surface evaluation and electrochemical behavior of cerium conversion coating modified with silane on magnesium alloy.

A new cerium conversion coating modified with the hydrolysis silane is designed for AZ31 magnesium alloy, which aims at assessing the surface characterizations and electrochemical behaviors between the cerium conversion coating with and without the silane modified. The effect of the silane addictive is studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The adhesion of the coatings is undertaken according to the American Society for Testing and Materials (ASTM) standard D3359-08 cross tape test. The electrochemical behavior is evacuated by polarization experiment and electrochemical impedance spectroscopy (EIS) in NaCl electrolyte. The results show that the addition of bis-[triethoxysilylpropyl] tetrasulfide (BTESPT) to loosen and porous cerium conversion coating leads to the formation of a more compact and homogenous film, higher resistance to water uptake and better adhesion to substrate. Electrochemical measurements show that, compared with the non-modified cerium conversion coating, the coating modified with the silane exhibits better anticorrosion properties. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]