Corrosion behavior of AZ91D magnesium alloy in ethylene glycol aqueous solutions containing trace Cl− and Cu2+

Corrosion behavior of AZ91D magnesium alloy in 60% ethylene glycol aqueous solution containing trace Cl - and Cu 2+ were systematically investigated using weight loss measurements, white light interferometry, and electrochemical analysis. Key findings reveal that: Corrosion acceleration efficacy follows: [Cu 2+ ] < [ Cl - ] < [Cl - +Cu 2+ ]. Specifically, the corrosion rate in the coexistence of Cl - and Cu 2+ is 10.12% higher than that in the presence of Cl - alone; the depth and diameter of Q3 pits increase by 12.74% and 50.43%, respectively, manifesting that the coexistence of two ions primarily exacerbates pitting severity. Mechanistically, cathodically deposited Cu particles induce microcrack formation and form micro-galvanic couples with the Mg matrix, thereby accelerating the corrosion rate. Furthermore, the synergistic attack of Cl - and embedded Cu particles severely impairs the integrity of the corrosion product film, which sustains the galvanic acceleration effect of Cu particles and ultimately leads to intensified pitting corrosion.