Hot-dip galvanized steel pipes are widely used in construction, machinery, coal, chemical, railway vehicles, automobile industry, roads, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, mining machinery and other GI galvanized steel pipe manufacturing industries. The surface of the galvanized steel pipe is welded with hot dip or galvanized steel. Zinc plating can increase the corrosion resistance of steel pipes and prolong their service life. Galvanized pipes are widely used, in addition to pipelines for general low-pressure fluids such as water, gas, oil, etc., and also used as oil well pipes and oil pipes in the petroleum industry, especially in offshore oil fields, and oil heaters and condensation of chemical coking equipment. Cooler, coal distillate oil exchanger pipe, and trestle pipe pile, support pipe for mine tunnel, etc.
The following content explains the protection principle of the galvanized protective layer of hot-dip galvanized steel pipe.
The reason why the steel pipe is hot-dip galvanized is because zinc can form a corrosion-resistant film on the surface in a corrosive environment. It not only protects the zinc layer itself, but also protects the steel base, but its service life and its environment This can be confirmed by an atmospheric corrosion test on hot-dip galvanized steel pipes.
Hot-dip galvanized steel pipes have different corrosion rates in different environments. Theoretically, this corrosion can be divided into two different ways, namely chemical corrosion and electrochemical corrosion.
Chemical Corrosion: The direct chemical action of the metal with the surrounding medium, such as dry (absolutely no moisture) gas and non-conductive liquid medium (non-electrolyte), the chemical action on zinc is called typical chemical corrosion.
Electrochemical corrosion refers to the corrosion of metals in humid gases and in conductive liquid media (electrolytes) due to the flow of electrons. For example, corrosion of zinc in acids, bases, salt solutions and seawater, and atmospheric corrosion of zinc in humid air are all electrochemical corrosion.
The electrolyte is formed when moisture in the air accumulates in the pits on the surface of the galvanized sheet, and carbon dioxide, sulfur dioxide or other corrosive medium in the air dissolves in the water.