Explanation for anomalous environmentally assisted cracking behaviour of a wrought Mg-Mn alloy in chloride medium

•Arsenate ions lower pitting corrosion and increase repassivation tendency of a wrought Mg-Mn alloy in 0.6 M chloride solution.•Arsenate ions help in increasing elongation to failure in SSRT tests in chloride medium by ∼45%.•By promoting oxide film stability, cathodic charging raises EAC resistance of the alloy.

The role of arsenate ions and cathodic charging on the environmentally assisted cracking (EAC) behaviour of a Mg-Mn alloy in 0.6 M NaCl saturated with Mg(OH)2 was investigated. The stability of the surface film and the repassivation kinetics have been found to play a critical role in the EAC tendency of the alloy than hydrogen-assisted mechanisms. Cathodic charging was found to be beneficial in lowering the EAC tendency of the alloy.