Aluzinc steel sheet features a distinctive smooth, flat, and decorative spangle surface with a silver‑white base colour. Its unique coating structure provides excellent corrosion resistance. With a normal service life of up to 25 years, it also offers outstanding heat resistance, withstanding temperatures up to 315°C. The coating exhibits strong adhesion to paint films, good workability (including stamping, shearing, and welding), and high surface conductivity.
The coating composition, by weight, consists of 55% aluminium, 43.4% zinc, and 1.6% silicon. The production process is similar to that of galvanized and aluminised sheets, using a continuous hot‑dip coating method. When both sides are exposed to the same environment, 55% Al‑Zn alloy‑coated steel offers significantly better corrosion resistance than galvanized steel of the same thickness. In addition to its excellent corrosion resistance, the pre‑painted products derived from this coating also provide outstanding adhesion and flexibility.
Key differences between galvanized steel and aluzinc steel:
The primary difference lies in the coating material. Galvanized steel has a uniform layer of pure zinc on the surface, which protects the base metal through anodic (sacrificial) protection. In other words, the zinc corrodes preferentially, shielding the underlying steel; only after the zinc is entirely consumed will the base metal be attacked.
In contrast, the aluzinc coating is composed of 55% aluminium, 43.4% zinc, and minor alloying elements. Under microscopic observation, the coating exhibits a honeycomb structure, where aluminium "cells" encapsulate zinc particles. While this coating also provides some anodic protection, the effect is greatly reduced – partly because of the lower zinc content, and partly because the zinc is enclosed by aluminium, which hinders electrolytic action. Consequently, when an aluzinc sheet is cut, the exposed edges lose most of this protection and can corrode rapidly. Therefore, it is advisable to minimise cutting of aluzinc sheets; whenever cutting is necessary, the edges should be sealed with anti‑rust or zinc‑rich paint to extend the service life of the material.
