Structure–property quantification of corrosion pitting under immersion and salt-spray environments on an extruded AZ61 magnesium alloy

Extruded AZ61 magnesium coupons were exposed to immersion and cyclical salt spray environments over 60 h in order to characterize their corrosion rates. The characteristics of general corrosion, pitting corrosion, and intergranular corrosion were quantified at various intervals. General corrosion was more prevalent on the immersion surface. In addition, more pits formed on the immersion surface due the continuous exposure to water and chloride ions. However, the pits on the salt spray surface showed larger surface areas, larger volumes, and covered more area on the micrographs as compared to the pits on the immersion surface, due to the dried pit debris that trapped chloride ions within the pits.

Research highlights
► AZ61 corrosion mechanisms in two environments were studied.
► General corrosion and surface characteristics were higher in the immersion environment.
► Pit characteristics, such as surface area and volume, were larger on the salt spray surfaces.
► The continuous presence of water affected the general corrosion and pit formation.
► The build-up of chloride ions affected pit growth on the salt spray surfaces.