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.