连续热镀锌是彩钢卷的质量缺陷及对策

连续镀锌彩钢卷锌层剥落（附着氧化物）
连续镀锌彩钢卷形式：镀锌层容易脱落（大块或小块）。剥离下基材表面有氧化，呈黑色、蓝色或黑蓝色混合。一般在剥皮前，镀层会形成针孔状，镀层的表面形貌也会出现视觉异常（锌花立体突出，表面特别光亮等）；

Spalling of zinc layer (attached oxide)

Form: the zinc coating is easy to peel off (large or small pieces). There is oxidation on the surface of the substrate under the stripping, which is black, blue or black blue mixed. Generally, before peeling, the coating will form pinhole shape, and the surface morphology of the coating will also appear visual abnormalities (zinc flowers are three-dimensional protruding, the surface is particularly bright Etc.);
When the production line is shut down for some reason, if the atmosphere of the non oxidation furnace is not well controlled, the steel surface will form peeling oxide scale. When this part passes through the zinc pool and is blown off by air knife, the exposed black spots will be formed. Besides floating out of the zinc bath, some of the blown off rust skin may also be suspended in the zinc bath, which usually takes a long time to bring out all the rust.
Cause of formation: can be divided into furnace area and non furnace area factors
Furnace area factors:
-Improper control of air / gas combustion ratio and flow rate leads to improper CO and O2 content in furnace atmosphere
-The furnace temperature is too low or improperly matched with the plate temperature, and the plate temperature is too low
-The dew point is too high, that is, the water content (H2O) is too high
-The sudden change of plate temperature results in the excessive change of furnace temperature And so on
Non furnace area factors:
-Poor cleaning
-The water quality in the washing section is not good
Countermeasures:
a) Prevent air leakage in furnace area
b) Prevent leakage of cooling water system in furnace area
c) Carefully and properly control the atmosphere co%: 3 - 5%, furnace temperature > 1200 ℃
d) Proper control of alkali washing conditions: free alkali, alkali ratio, alkali washing temperature
e) When the water quality is poor, open the bypass soft and pure water manual valve
f) When the reaction between H2 and steel plate is poor, the plate temperature can be increased to promote the reduction rate or decrease the rate to increase the reaction time