Assessment of Some Advanced Protective Schemes, Including Chromate and Non-Chromate Conversion Coatings for Mg Alloy ZE41A-T5 Using Electrochemical Impedance Spectroscopy

摘要

A study has been conducted to evaluate the suitability of a non-chromateconversion coating (Tagnite 8200) for replacing the currently used chromate conversion coating (Dow 17) on Mg alloy ZE41A-T5 This replacement must be accomplished without compromising the corrosion resistance and protection efficacy of other advanced coating schemes. Electrochemical Impedance Spectroscopy (EIS) and salt spray tests have been employed to compare the corrosion behavior in chloride containing solutions of Mg alloy ZE41A-T5 which has been coated with various combinations of a conversion coating (Tagnite 8200 or Dow 17), primer (Sermetel 1083 or epoxy) and topcoat (Sermetel 1089, polyurethane, or epoxy electrodeposited E-coat). Results indicate that there are several coating schemes which perform better than the currently used system armed that the EIS and the salt apray tests show a direct correlation.