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What are the characteristics of steel corrosion

Update:14 Sep 2018
Summary:

Color coated plates, color steel plates, color coated s […]

Color coated plates, color steel plates, color coated steel coil , and colored steel coils are exposed to the atmosphere. There are several cases of dry corrosion, wet turbidity and wet corrosion.
Dry corrosion of steel refers to the corrosion of steel without a continuous electrolyte water film on the surface at a relative humidity of 4 and 30%. In this case, the galvannea corrosion rate is very slow, but this is less.

The wet corrosion of steel refers to the corrosion of steel in an atmospheric environment with a relative humidity of more than 30% and less than 100%. In this case, there is dust on the surface of the steel, and the rust layer has the pores and cracks to cause microscopic adsorption, forming a water film that is invisible to the naked eye, and electrochemical corrosion occurs under the water film, and the corrosion speed is relatively fast.

Wet corrosion of steel refers to the corrosion of steel in a humid atmosphere with a relative humidity greater than 100%, with a condensed, visible water film on the surface. In this case, the surface of the steel is thicker, so that the oxygen diffuses to the steel surface at a slower rate, which reduces the rate of corrosion.

In fact, the corrosion of steel is inseparable from the water film on its surface. It is because of the water, the oxygen is dissolved in the water, and the iron is ionized, and a series of ionization reactions occur.

The oxygen in the air is continuously dissolved in the water, and the reaction proceeds continuously. Since the main product of the reaction, Fes Oa, is red, the product after iron oxidation is generally called "red rust". The red rust is very loose and easy to dissolve. It is difficult to protect the steel surface from continuing to corrode, so that the corrosion of the steel continues until it is completely corroded. This is a characteristic of steel corrosion, which is why steel must be coated with other metal or non-metallic protective layers to effectively prevent corrosion of steel.