Under what conditions is the FezA1a intermediate phase layer formed in galvanizing?
Generally speaking, the higher the absorption of AL in the alloy layer, the better the adhesion of the coating;And alloy layer of AL uptake depends not only on aluminum content in liquid zinc, and in a greater extent in the strip temperature of zinc immersion fluid, so in the modern strip continuous production line, strip temperature is higher than general requirements zinc liquid temperature 20 ℃ or so.Because the enthalpy of fe-al from one to another is greater than the enthalpy of fe-al.In addition, since AL has a greater affinity to iron than Zn, fe-al compounds are superior to fe-zn compounds.The superproportionally large amounts of aluminum are absorbed from the Zn solution, and the resulting ferro-aluminum compounds (FeAls) concentrate directly on the strip's surface, a process that goes on until it is below the temperature required for the reaction and diffusion.This thin, homogeneous interphase layer can be firmly attached to the surface of the steel base, acting as the intermediate of the adhesive layer.
It can be seen that the forming conditions of FeA1 are as follows: certain zincification temperature, zincification time, and certain AL content in the zinc solution must be achieved.
How do you verify the existence of FeaAlo?
In recent years, a variety of methods have been established to study the structure and thickness of the mesophase. The most effective methods are: electrochemical separation, electron ray microanalysis, scanning electron microscopy and ion mass spectrometry.
What causes poor adhesion during production?
There are two main reasons for poor adhesion during production:
(1) Fe2Al, which has no adhesion media, is characterized by a thin alloy layer but poor adhesion of the coating layer, which can be tempered.
(2) FeAl, the intermediate phase layer is damaged. This product is characterized by a thick alloy layer, which cannot be attacked.