The influence of Mg/Al ratio on the cracking resistance of Zn–Al–Mg coatings

Galvanized steel plates with Zn–Al–Mg coatings are extensively utilized due to their exceptional corrosion resistance. This study, focusing on the cracking behavior of coatings with varying Mg/Al ratios, was conducted using in-situ tensile tests on different samples. The influence of the Mg/Al ratio on the crack resistance of the sample coatings was systematically summarized. To elucidate this point, five types of Zn–Al–Mg coatings with varying Mg/Al ratios were prepared using the same galvanizing process and tensile testing performed using a scanning electron microscope equipped with in-situ tensile capabilities. Macroscopic digital image statistical techniques were employed to quantify the extent of coating cracking, demonstrating the impact of the Mg/Al ratio on the coatings' crack resistance. The findings suggest that an increase in the Mg/Al ratio deteriorates the crack resistance of the coating, while enhancing its hardness. Moreover, this research offers a novel perspective in evaluating the crack resistance of coatings by comparing the effects of different Mg/Al ratios.