Study on corrosion behavior of as‐extruded AZ80 magnesium alloy sheet in wet hydrogen sulfide atmosphere

Abstract

In this work, the corrosion behavior, including corrosion morphology, corrosion rate, corrosion residual strength, and fracture characteristics, of as‐extruded AZ80 magnesium alloy sheets in a wet hydrogen sulfide atmosphere was investigated by macro‐observation, optical microscopy, scanning electron microscopy, confocal laser scanning microscopy, X‐ray diffraction, and tensile testing. The results revealed that the corrosion rate gradually decreased with a longer exposure time. The corrosion process included corrosion pits that initiated on the surface, expanded and became deeper by layer denudation, and then coalesce and connected together. XRD patterns showed that the corrosion products were mainly composed of magnesium hydrate and magnesium sulfate dihydrate. The concentration of stress and the high crack sensitivity at the bottom of the corrosion pits were the main reasons for the drop in corrosion residual strength and ductility at the early stage of the corrosion process. However, with increasing exposure time, both the residual strength and ductility decreased very slowly and even reached a stable state. In addition, variations in the corrosion residual strength and ductility could be described by an exponential decay function throughout the corrosion test.