An alloy layer is a metallic layer formed by a chemical reaction in which two different metals bond and mix at the molecular level.

Its thickness and properties vary with the duration of the plating process.

As a general rule, a slower plating process results in a thicker alloy layer, while a faster process results in a thinner one. If the alloy layer is too thick, its structural integrity becomes unstable, potentially leading to coating peeling or delamination.

In hot-dip galvanizing, the coating consists of two distinct layers: the alloy layer, where iron and zinc are intermingled, and the pure zinc layer, composed solely of zinc.

The anti-corrosion performance is determined not by the alloy layer, but by the thickness of the pure zinc layer.

Essentially, because the regions where iron and zinc are mixed contain iron that can rust, the alloy layer remains a factor in long-term corrosion resistance.