The corrosion behavior of AZ91D magnesium alloy in simulated haze aqueous solution

Abstract

The corrosion process of AZ91D magnesium alloy in simulated haze aqueous solution has been studied by electrochemical measurements, immersion tests and morphology characterization. Results show that AZ91D was corroded heavily in simulated haze aqueous solution due to the loose and breakable product film on the surface providing little corrosion barrier. The effect of different ions was investigated. It was found that both NO3- and NH4+ played an important role in the corrosion process. NO3- helped to form passive film to protect the matrix, yet NH4+ consumed OH-, resulting in the absence of Mg(OH)2 and serious corrosion. Meanwhile, SO42- and Cl- had influence on pitting corrosion. Magnesium aluminum oxide and MgAl2(SO4)4·22H2O instead of Mg(OH)2 were the dominate products, which is different from the former study. Corrosion rate changed with time, especially in the first 3 h. A two-stage corrosion mechanism is proposed after considering both the corrosion process and the influence of ions.