A ceria based conversion coating on squeeze cast Mg- 4wt. %Y alloy for improved corrosion resistance in 0.1 M NaCl solution

Abstract

Introduction: Magnesium (Mg) It has high specific strength, excellent damping capabilities, good castability, excellent machinability, good electromagnetic shielding, and recyclability.However, Mg has poor high temperature mechanical properties (creep) and limited salt-water corrosion resistance, which decreases its widespread application in engineering materials. Objectives : Development of Mg based alloys using Y as alloying addition within their permissible maximum solid solubility limits by squeeze casting. ; Determine the microstructures and mechanical properties; Perform Cerium conversion coating (CeCC) on Mg-4wt.%Y samples for different time periods; Examine the influence of surface films formed on Mg alloys by open-circuit corrosion in 0.1 molar NaCl solution by electrochemical and immersion corrosion methods. Conclusions : Mg-4 wt.% Y alloy was developed y using the bottom pouring squeeze casting set-up. XRD pattern and EDX confirmed the presence of α-Mg and Mg24Y5 phases in the casted alloy. The samples of the ingots were coated using the CeCC for different time periods of 30s, 60s, 120s and 1800s; FESEM-EDX revealed that the Cerium concentration increased with the coating duration and also the coating had been locally damaged with several dry-mud like crisscrossed cracks; CeCC for 30s demonstrated improved corrosion resistance than the bare and other CeCC coated samples for longer duration during immersion and electrochemical corrosion test.