Effect of heat treatment of magnesium alloy substrates on corrosion resistance of a hybrid organic-inorganic sol-gel film
2015
Diaz, L. | García Galván, Federico | Llorente, Irene | Jiménez-Morales, Antonia | Galván Sierra, Juan Carlos | Feliú Jr., S. | Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
The influence of heat treatment of magnesium alloy substrates on corrosion resistance of a sol¿gel coating has been assessed during immersion tests in 0.6 M NaCl aqueous solution. Relative differences in the chemical nature of the layers were quantified by scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDX). Corrosion behaviour was evaluated by Electrochemical Impedance Spectroscopy (EIS) and hydrogen evolution measurement. Long-term immersion testing show that the sol¿gel/heat treated AZ61 substrate exhibits a superior anti-corrosion property in comparison with the sol¿gel/non-heated substrate. In contrast, no significant changes have been observed between the heated and non-heated samples in the case of the sol¿gel coated AZ31 substrates. A link was found between lower O/Si atomic ratios observed by EDX analysis on the sol¿gel coatings after the preparation process and reduced corrosion upon the coated substrates. Heat-treatment increased the protective properties of the passive film on the surface of the AZ61 substrate and hence inhibited magnesium dissolution and hydrophilic group formation during coating preparation.
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