Localized Corrosion of Binary Mg–Ca Alloy in 0.9 wt% Sodium Chloride Solution

To further understand the localized corrosion of magnesium alloy, various in situ electrochemical techniques and ex situ electron microprobe analysis and SEM were used to monitor the corrosion process of Mg–1.0Ca alloy in 0.9 wt% sodium chloride solution. The results indicated that the localized corrosion was accompanied by the formation and thickening of a corrosion product film on the Mg–1.0Ca alloy. A localized corrosion of the alloy initiated selectively on the eutectic micro-constituent zones, then enhanced with the exposure, developed in depth with ring-shaped corrosion products accumulated around and finally formed a volcanic-like pitting. Based on the measurements, an electrochemical corrosion model was proposed accordingly to describe the formation mechanism of the volcanic-like pitting on the alloy in 0.9 wt% sodium chloride solution.