Unveiling the Atmospheric Corrosion Behavior of Die-cast AZ91D Magnesium Alloy: From Mechanism to Laboratory-to-Field Test Correlation

Abstract The application of Mg alloy components in automobiles enables significant weight reduction. However, the poor corrosion resistance of Mg alloys remains a critical impediment. Moreover, their corrosion mechanisms and modes are fundamentally different from those of conventional materials such as steel and aluminum. Currently, the automotive industry lacks well-established accelerated corrosion testing and evaluation methodologies specifically tailored for Mg alloys. In this study, the corrosion behavior of die-cast AZ91D Mg alloy was systematically investigated under three distinct exposure conditions, including marine atmosphere, proving ground vehicle corrosion test (PGVCT) and various laboratory corrosion environment. The corrosion performance was evaluated in terms of morphology, weight loss rate, and corrosion depth, based on which the atmospheric corrosion mechanism was elucidated and a laboratory-to-field corrosion test correlation was established for the magnesium alloy. This work provides a critical foundation for developing highly relevant accelerated corrosion test method for Mg alloys used in automotive applications.