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Why Can Adding Aluminum To Zinc Solution Improve The Adhesion Of Coating?

- Dec 27, 2018 -

In modern hot dip galvanizing, why do you want to put aluminum in the liquid?

In the modern hot galvanizing process, a certain amount of aluminum is often added to the zinc solution. After adding aluminum to the zinc solution, the quality of the galvanized layer is greatly improved, which is shown in the following aspects:

(1) zinc solution containing 0.1 ~0.2% aluminum, can significantly improve the luster of the coating, because aluminum has a large affinity to oxygen, zinc contains aluminum, can avoid zinc oxidation caused by the coating yellowing phenomenon.

(2) when the aluminum content in zinc solution is 0.10 ~ 0.15%, the adhesion of zinc coating can be significantly improved so that the coating has good plasticity and does not fall off.

(3) when the zinc solution contains 0.15 ~ 0.20% aluminum, the coating structure can be significantly changed: iron and zinc alloy layer 5, phase and phase 5 (FeZns3) thin or even completely disappear to obtain n relatively thick coating.

(4) when the zinc solution contains 0.14~ 0.16% aluminum, the bottom slag in the zinc pot can be eliminated, while Fe2Als is relatively small, floating on the surface of the zinc solution and can be eliminated at any time without stopping production.

Why can adding aluminum to zinc solution improve the adhesion of coating?

Because of aluminum and iron affinity than zinc and iron reaction of affinity, so, when the strip into the liquid zinc containing aluminum, on the strip surface forming Fe2A1 or FeAl first, than the melting point of this iron compound aluminum zinc liquid temperature is high, will not immediately in liquid zinc melting, and takes on the form of a thin film firmly adhere to 40 on steel strip surface, hinder the normal reaction of zinc, iron with impeded, zinc iron response generated when galvanized iron zinc alloy layer thinned a especially 5 subtraction thin brittle, 5 the thinner, the adhesion of zinc layer is better.

What is the mechanism of action of aluminum in zinc solution during galvanizing?

Because of aluminum and iron affinity than zinc and iron reaction of affinity, so, when the strip into the liquid zinc containing aluminum, formed in the strip surface first Fe2A1: or FeAl, than the melting point of this iron compound aluminum zinc liquid temperature is high, will not immediately in liquid zinc melting, and takes on the form of a thin film firmly clung on steel strip surface, hinder the normal reaction of zinc, iron with impeded, zinc iron response generated when galvanized iron zinc alloy layer thinned a especially 5 subtraction thin brittle, 5 phase the thinner, the zinc layer adhesion