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What factors are related to the formation of FezAls or FeA1s intermediate phase layer in hot galvanizing?

- Jan 02, 2019 -

What factors are related to the formation of FezAls or FeA1s intermediate phase layer in hot galvanizing?

The formation of the middle phase layer between aluminum and iron is related to the aluminum concentration in zinc solution, galvanizing time and the temperature at which the strip is put into the zinc pot. The influences are described as follows:

(1) affected by the concentration of aluminum in zinc solution: the aluminum content in the alloy layer of the coating increases with the increase of aluminum content in zinc solution. If the zinc solution does not contain aluminum, there is no material basis for the reaction and fe-a1 intermediate phase layer cannot be formed.

2) affected by galvanized time: generally speaking, the aluminum content in the coating increases with the extension of galvanized time, because the extension of galvanized time, is equal to increase the opportunity of aluminum in zinc solution to the diffusion of the coating.

(3) influenced by the temperature of the strip: the temperature at which the strip enters the zinc pot has a great influence on the formation rate of aluminum and iron compounds when the strip is hot-galvanized with sengiemil. If the temperature at which the strip enters the zinc pot is appropriately higher than the operating temperature of the zinc pot, the aluminum concentration in the alloy layer can be increased and the adhesion of the zinc layer can be improved.Effect of aluminum in zinc solution on the thickness of pure zinc layer?

The aluminum content in the zinc pot is generally less than 0.2%, and adding aluminum in the range of 0.0~0.2% will reduce the fluidity of zinc solution, so the increase in aluminum content will increase the thickness of pure zinc layer, while the pure zinc layer is relatively flexible and not easy to fall off when bending.

Effect of aluminum in zinc solution on Cuso corrosion resistance of coatings?

As the aluminum in the zinc solution thicken the n phase, the alloy layer becomes thinner and even disappears. Therefore, the corrosion resistance of the coating to CusO declines. For CusO resistant materials, fe-zn alloy layer is often expected to thicken.