Comparison of Corrosion Resistance Characteristics of Zn-Al-Mg Alloy Steel according to Cutting Methods

Abstract

The cutting method plays a critical role in determining the cut-edge quality and corrosion resistance of Zn–Al–Mg alloycoated steel. This study systematically compared the corrosion behavior at cut edges produced by different cutting processes. Plasma cutting caused oxide formation and partial evaporation of the zinc layer, resulting in darkened cut surfaces and rapid initial red rust formation due to loss of sacrificial protection. Shear cutting induced localized mechanical deformation and coating damage, leading to progressive corrosion initiation at damaged regions. In contrast, waterjet cutting produced clean cut edges with minimal thermal and mechanical damage, thereby maintaining surface stability and delaying corrosion. Gradual color changes during exposure indicated the formation of corrosion products associated with oxidation and self-healing behavior. Overall corrosion resistance followed the order: waterjet > shear > laser > plasma cutting. These results demonstrate that minimizing thermal and mechanical damage at the cut edge is essential for preserving the sacrificial protective function of Zn–Al–Mg coatings. Accordingly, waterjet and precision shearing are recommended for marine and outdoor structural applications.