Effect of Synthesizing Temperature on Microstructure and Electrochemical Property of the Hydrothermal Conversion Coating on Mg-2Zn-0.5Mn-Ca-Ce Alloy

Abstract

Mg(OH)2 conversion coatings were formed on an Mg-2Zn-0.5Mn-Ca-Ce alloy via hydrothermal method at three different synthesizing temperatures (160, 170 and 180 °C). The effect of synthesizing temperature on microstructure and electrochemical property of the coatings were systematically studied. With increasing synthesizing temperature, the coating became thicker due to the faster reaction and deposition of Mg(OH)2 on the α-Mg phase and secondary phases of the substrate Mg alloy. Internal micro-cracks were also generated in the higher-temperature synthesized coatings due to the increased shrinking stress, but the cross-cutting micro-cracks were suppressed. Benefiting from the improved barrier effect against penetration of corrosive medium, the higher-temperature synthesized thicker coating presented significantly enhanced electrochemical property and anti-corrosion efficiency in Hanks’ solution.