The Science Behind 55% Al‑Zn Performance
The superior corrosion resistance of Galvalume lies in its unique solidification microstructure. The coating consists of an aluminum‑rich dendritic phase occupying ~80% of the volume, with a zinc‑rich interdendritic network. This two‑phase structure creates a synergistic protection mechanism.

Corrosion Protection Mechanisms

• Barrier Layer: The aluminum‑rich phase rapidly forms a dense, adherent alumina (Al₂O₃) film that is stable in pH 4‑9 environments, acting as a physical barrier.

• Galvanic Protection: The zinc‑rich phase sacrifices itself to protect cut edges and scratches. As zinc corrodes, it deposits zinc corrosion products that migrate and cover exposed steel.

• Cut‑Edge Behavior: While GL cut edges may show initial red rust (unlike ZAM), the aluminum oxide barrier quickly slows corrosion creep, and the zinc sacrificial action limits undercutting. In most atmospheric exposures, cut‑edge performance is adequate and far superior to paint‑only protection.

Product Parameters

• Dendrite Spacing: Influenced by bath temperature and cooling rate; finer spacing improves corrosion distribution.

• Silicon Role: 1.6% Si in the bath suppresses excessive Fe‑Al intermetallic growth at the steel‑coating interface, ensuring good adhesion.