Galvanized vs Aluminized Steel: Corrosion Resistance and Performance
Differences Between Galvanized and Aluminum-Coated Sheets
1. Galvanized Sheet
Galvanized sheets, commonly used in various applications, have the thinnest compound layer among the three coatings, and their thickness is easy to control. Adding a small amount of aluminum allows the coating to be even thinner, improving processing performance. The corrosion resistance of a galvanized sheet depends largely on the coating’s integrity. When intact, the galvanized layer provides some protection. However, if the coating corrodes, it cannot form a protective oxide layer.
Once scratched, the galvanized layer relies on electrochemical protection. The zinc coating, when exposed, forms a primary battery with the steel base in a humid environment. The zinc oxidizes, sacrificing itself to protect the steel underneath, until the coating is fully corroded. For better performance in high-corrosion environments, aluminized steel is often recommended due to its superior resistance.
2. Aluminum-Plated Sheet
Aluminum-coated sheets, including aluminized steel, are similar to hot-dip galvanized sheets but have a thicker compound layer. The outer layer is pure aluminum, while the inner layer consists of an iron-aluminum compound. The diffusion and chemical reaction between liquid aluminum and solid iron are intense, resulting in a thick compound layer that is difficult to control. This affects its processing, as the coating can crack or peel during stretching or deep drawing.
Aluminum coatings offer strong corrosion resistance as long as they remain intact. The dense protective film on the aluminum surface prevents further corrosion, even under harsh conditions. Aluminized steel is also known for its excellent heat resistance, which is comparable to stainless steel and can withstand temperatures up to 450°C. However, if scratched, the aluminum coating loses its protective properties. Though the coating offers some cathodic protection, the dense oxide layer weakens the sacrificial protection effect, leading to corrosion of the steel base.
When comparing aluminized steel and galvanized sheets, the choice often depends on the required strength, temperature tolerance, and corrosion resistance. The aluminized steel price might vary based on these factors, but its durability often makes it a cost-effective choice for high-temperature and corrosive environments.
If you’re looking for a reliable aluminized steel supplier, it is important to consider these characteristics to make the best decision for your specific needs.
