Atmospheric corrosion of field-exposed AZ31 magnesium in a tropical marine environment

• Variation of Cl− deposition rate results in a fluctuation of corrosion rate.
• Pitting corrosion occurs at the initial stage and then shifts to general corrosion.
• Mg5(CO3)4(OH)2·xH2O dominates the corrosion products during the exposure periods.
• Protectiveness of corrosion products depends on their structure and exposure time.

Corrosion behavior of AZ31 magnesium in tropical marine atmosphere was investigated. Chloride ions deposition rate played an important role in the corrosion process, which resulted in an obvious fluctuation of the corrosion rate. The corrosion was initiated from pitting corrosion and then evolved into general corrosion as the exposure time extended. Mg5(CO3)4(OH)2·xH2O was the dominate products during the whole exposure periods. The products on the specimens weathered for 1, 6 and 12 months slightly suppressed the corrosion process, while that generated after 24 months of exposure exhibited good protective ability against further corrosion attacks.