Corrosion characteristics of galvanized steel sheet

When the galvanized steel sheet is exposed to the air, it is critical to produce dry erosion, wet cold erosion and wet erosion. The dry corrosion of China PPGI corrugated roofing sheet manufacturer means that the surface layer of the steel in ambient air with an air humidity of less than 30% does not produce a continuous corrosion of the electrolyte water film. Under such circumstances, the corrosion rate of steel is relatively slow. But such natural environment standards are too few. The wet cold etching of galvanized steel sheet refers to the corrosion of steel in ambient air with an air humidity of more than 30% and less than 100%. Under such circumstances, there is dust on the surface of the steel, and there are micropores and gaps in the rust layer, which causes the microscope to absorb, produce shrinkage water that is invisible to the human eye, and generate the principle of a galvanic cell under the shrinkage water. The erosion rate is relatively rapid. . Wet erosion of galvanized steel sheet refers to the erosion of China PPGI corrugated roofing sheet factory in the cold and cold ambient air with an air humidity of more than 100%, when the surface has solidified shrinkage water visible to the human eye. Under such circumstances, the shrinkage water of the steel surface layer is too thick, so that the rate of diffusion of oxygen out of the steel surface layer after the melting of oxygen is relatively slow, which reduces the rate of erosion. In fact, the corrosion of steel is closely related to the shrinkage water in the surface layer between the two. It is because there is water, and the water dissolves co2, so that the iron produces a weak electrolyte and produces a series of weak electrolyte reflections. The co2 in the gas continues to melt in the water, and the reaction continues. Because the key product reflected is bright red, the material after iron air oxidation is generally called "red rust". Red rust is very loose, it is very easy to melt, and it is impossible to maintain the surface of the steel without erosion again, which promotes the erosion of the steel until it is completely eroded. It is a characteristic of steel. Because of this, the steel must be coated with other metal materials or the thickness of the protective layer of metal materials in order to reasonably avoid the corrosion of the steel.