Corrosion resistance and characterization studies of calcium series chemical conversion film via green pretreatment on magnesium alloy

Abstract

Purpose

Magnesium alloys, although valuable, are reactive and require protection before its application in many fields. The purpose of this study was to evaluate a novel anticorrosive chemical conversion film on AZ80 magnesium alloy by environmental-friendly calcium series surface pretreatment.

Design/methodology/approach

The corrosion resistance of the film was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 Wt.% NaCl solution. The surface morphologies, microstructure and composition of the film were investigated by scanning electron microscopy and energy-dispersive spectroscopy.

Findings

The corrosion current density of the calcium series film decreased by more than one order of magnitude as compared to that of the AZ80 magnesium alloy. The conversion film presented dry-mud morphology, and its thickness was estimated to be approximately 4 μm. The conversion film was highly hydrophilic, and the organic coating adhesion on treated AZ80 surface was approximately 13.5 MPa.

Originality/value

Excellent performance of the calcium-based chemical conversion film on Mg alloy was obtained, which does not contain heavy metals or fluorides and completely conforms to European RoHS (Restriction of Hazardous Substances) standard.

Citation

Wu, F., Liu, X. and Xiao, X. (2016), "Corrosion resistance and characterization studies of calcium series chemical conversion film via green pretreatment on magnesium alloy", Anti-Corrosion Methods and Materials, Vol. 63 No. 6, pp. 508-512. https://doi.org/10.1108/ACMM-10-2015-1588