When hot lead plating can make a solid bond between steel and paint; hot galvanizing can increase the chemical stability and surface gloss of steel, and effectively reduce the gradient of steel surface potential. However, it reduces the corrosion resistance of steel due to oxidation of its surface, which leads to weakened adhesion of steel to paint and metal. At the same time steel is coated with zinc alloy in which the zinc will evaporate from the steel surface at a certain degree of melting point resulting in a reduction in the thickness of the zinc film. Hot-dip galvanizing is prone to secondary pollution of steel due to the poor thermal stability of zinc powder, while its corrosion resistance is poor.
There are many types of surface treatments for hot-dip galvanized steel pipes. Generally, they can be divided into pre-plating treatment and post-plating treatment. The pre-plating treatment is divided into cold galvanizing and hot-dip galvanizing. Cold galvanizing is the process of galvanizing by spraying zinc salts on the surface of the steel pipe; post-plating treatment is divided into pickling with alkali neutralization, chemical passivation (pickling), etc. The surface treatment process of hot-dip galvanized steel pipe includes sandblasting and shot blasting and chemical etching treatment.
The zinc layer is evenly distributed inside the steel through the hot-dip galvanizing layer, and the galvanized layer is closely integrated with the base material to enhance its corrosion resistance; the chemical bonding between copper ions and zinc ions in the hot-dip galvanizing layer forms a zinc-containing coating layer, which has strong adhesion to the metal and can interact electrochemically with the steel pipe; the galvanized layer forms a dense and hard zinc alloy layer with the steel surface. This composite galvanized layer has an extremely strong corrosion resistance. Hot-dip galvanized steel waterproof casing manufacturer is introduced here, I hope it will be helpful to you.
