The compound layer is a common feature of the hot-dip plating process. Unlike the bonding force between the electroplated coating and the steel base is the attraction between atoms, the hot-dipped metal does not directly contact the steel base, but is bonded together by the formed compound. The compound is characterized by high hardness and poor plasticity. Therefore, the presence of this layer of compound greatly affects the processing performance of hot-dip products during bending and deformation and the subsequent anti-corrosion performance.
Among the three coatings of hot-dip galvanizing, aluminum-plating, and aluminum-zinc alloy plating, the compound layer of hot-dip galvanizing is very thin, and it is easy to control its thickness; it can be thinner after adding a small amount of aluminum, so The processing performance is better at this time.
When the coating is intact, the anti-corrosion performance of the zinc coating is not the best, because the product after corrosion is very loose, and a dense oxide film protective layer cannot be formed to protect the internal organization, but it can basically meet various purposes The anti-corrosion performance of the galvanized layer has been greatly improved, especially after the passivation treatment.
After the coating is scratched and the steel base is exposed, the sacrificial anti-corrosion effect of the zinc coating shows its superiority. After the coating is scratched, the physical protection of the coating on the steel base disappears, and it depends on the electrochemical protection. Although zinc oxide is not very dense, this sacrificial anticorrosion effect is strong, and it can protect the steel base until the zinc coating is completely corroded.