What are the characteristics of structure and anti-corrosion properties of hot-dip galvanized coating

Compound layer is the common characteristic of hot dip plating process. Unlike electroplating, where the binding force between the coating and the steel base is the attraction between the atoms, hot-dip plated metals are not in direct contact with the steel base, but are bound together by forming compounds. The compound is characterized by high hardness and poor plasticity, so the existence of this layer of compound will greatly affect the machining properties of hot-plated products in the process of bending deformation and later corrosion resistance.

In the three kinds of coating, hot dip galvanizing, aluminum plating, aluminum plating zinc alloy, the compound layer of hot dip galvanizing is very thin, but also very easy to control its thickness; After the addition of a small amount of aluminum can be thinner, so the processing property is better.

In the case of intact coating, the corrosion resistance of galvanized layer is not the best, because the products after corrosion are very loose, can not form a dense oxide film protective layer to protect the internal organization, but also can basically meet the needs of various uses, especially after passivation treatment, the corrosion resistance of galvanized layer has been greatly improved.

After the coating is scratched and the steel base is exposed, the sacrificial anticorrosion function of zinc coating shows its superiority. After the coating is scratched, the physical protection effect of the coating on the steel base disappears, and it depends on the electrochemical protection effect. Although the zinc oxide is not very dense, this sacrificial action is strong and can protect the steel base until the zinc coating is completely corroded away.