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Home / News / Is the needle hole rate of hot dip galvanization related to alumina?

Is the needle hole rate of hot dip galvanization related to alumina?

source: 08.22,2018 author:Hebei Annuo

Since 2006, with the rapid increase of the price of zinc, in order to reduce the cost of hot dip galvanizing products, we have the hot dip aluminum plating production line in structure. However, no matter the structure of hot dip aluminum or hot dip galvanized aluminum alloy, the plating layer of pinhole leakage phenomenon began to increase, what is the cause of the pinhole leakage phenomenon?


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According to the expert analysis of the pinhole phenomenon in the coating, it is found that aluminum is a very active metal element. Before hot dip plating, even very small amount of oxide on the surface of iron and steel matrix will oxidize the contact aluminum atoms into alumina particles, which will reduce the infiltration of liquid aluminum and thus produce pinholes in the coating. In other words, it is alumina that causes pinholes. There are several reasons for producing alumina.

1. Incomplete degreasing; aluminum oxidation during oil combustion and decomposition;

2. The rust removal is not thorough, and the remaining oxide rust spots hinder the infiltration of the alloy melt, and the reduction reaction occurs to produce alumina.

Secondary oxidation occurs before hot dip due to low concentration of coplating agent or high dew point of protective atmosphere.

The drying temperature of the plated parts before hot dipping is low, which contains water or the drying temperature is too high, resulting in oxidation;

Then, in order to prevent the occurrence of pinhole leakage plating in hot dip galvanization, we generally adopt the strengthening process measures, among which the pretreatment is strengthened and the alloy melt is cleaned and added regularly. The most important thing is to adopt the purification technology to purify alumina without any dead Angle, and save time.


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