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What are the Characteristics of Galvanized Steel Sheet to Corrosion?

Apr. 13, 2020

Galvanized steel sheet refers to a thick steel sheet coated with a layer of zinc on the surface. Hot dip galvanizing is a frequently used economic development and reasonable anti-rust treatment method, about half of the world's zinc production is used for such processing technology. So what are the classifications of galvanized sheets and what are the corrosion characteristics of galvanized steel sheets, Galvanized Steel Sheet Manufacturer will come to tell you next.

According to the manufacturing, production and processing methods, it can be divided into the following types:

1. Hot Dipped Galvanized Steel Sheet. Infiltrate the cold-rolled steel sheet into the molten zinc bath

A cold-rolled steel sheet with a layer of zinc adhered to its surface. At this stage, the key is to use continuous hot-dip galvanizing process technology, that is, the thick steel plate is continuously immersed in the molten zinc plating bath to make galvanized steel;

2. Fine grain reinforced galvanized steel sheet. These thick steel plates are all manufactured by hot dip method, but they are heated to 500 ℃ immediately after being out of the tank to convert them into aluminum alloy plastic films of zinc and iron. This type of galvanized sheet has excellent adhesion of architectural coatings and weldability;

3. Electro-galvanized steel sheet. The production of this kind of galvanized steel plate by electroplating has excellent process performance. But the coating is thinner and the corrosion resistance is not as good as hot dip galvanized sheet;

4. Single-sided and double-sided galvanized steel sheets. Single and double-sided galvanized steel sheet, that is, hot galvanized products on only one side. In welding, spraying, rust prevention, production and processing, it has stronger adaptability than galvanized sheets on both sides.

What are the Characteristics of Galvanized Steel Sheet to Corrosion?

Galvanized Steel Sheet

When the Galvanized Steel Sheet is exposed to the air, there are several types of conditions such as dry etching, wet cold etching and wet etching.

The dry corrosion of galvanized steel sheet 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 the original cell under the shrinkage water. 

Wet erosion of galvanized steel sheet refers to the erosion of galvanized steel sheet in the cold and 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 to the outside 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 between the two layers. It is because of the presence of water, which melts co2, which makes iron produce a weak electrolyte and produce a series of weak electrolyte reflections.

The co2 in the gas continuously melts into 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 being eroded 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 corrosion of the steel.

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