Modification of a porous oxide layer formed on an Al–Zn–Mg alloy via plasma electrolytic oxidation and post treatment using oxalate ions
Abstract
This study investigated the surface modification of the oxide layer of an Al–Zn–Mg alloy via plasma electrolytic oxidation (PEO) followed by post treatment using oxalate ions. The samples were treated by PEO in alkaline-aluminate electrolyte with and without Na2C2O4. The post treatment was performed additionally by immersing the PEO-treated sample into Na2C2O4 solution. Upon PEO, the existence of oxalate ions would minimize the structural micro-defects. This was attributed to the formation of an oxalate-adsorption thin-film, generating soft plasma sparks after breakdown. Moreover, the oxide layer after post treatment using Na2C2O4 solution exhibited the crack-free structure desirable for suppressing the corrosion rate.