The reason why hot plating produces pinholes is explained in detail

Since 2006, with a sharp rise in the price of zinc, in order to reduce the rising cost of hot dip galvanizing products, in terms of structure and a lot of galvanized aluminum, 55% plus a lot of AI in the strip - zinc - 1.6 - SI coating production line, however, since 2010, whether structure hot dip aluminum, or steel strip hot 55 AI - zinc alloy plating, the plating pinhole in the phenomenon of leakage situation began to increase. In view of this phenomenon, various possible causes and industrial tests have been carried out, and the results show that the excessive AI2O3 inclusion in the original aluminum is one of the main causes of pinhole leakage plating in the hot coating containing aluminum.

Causes of pinhole in hot coating containing aluminum

Hot dip aluminum alloy melt contains more, because of the metal elements aluminum is already extremely lively, hot dip plating steel substrate surface before even trace amounts of oxidizing substances, will make contact with the liquid aluminum chloride particles, atomic oxygen produced by aluminum chloride particles reduced liquid aluminum embellish sex, so as to produce pinhole in the coating, iron matrix - the interface between aluminium liquid aluminium chloride of the existence of particles is the cause of the hot dip aluminized layer of pinhole, the findings have come as early as 1962.

During hot plating, the origin of A1O in bath solution is generally believed to occur in the following processes:

(1) incomplete degreasing and oxidation of aluminum during combustion and decomposition of grease;

(2) incomplete derusting, and the remaining oxide rust point hinders the infiltration of the alloy, as well as the emission reduction reaction to produce alumina;

(3) secondary oxidation occurs due to low concentration of plating AIDS or high dew point of protective atmosphere before hot dipping;

(4) oxidation occurs when the plating is dry at a low temperature containing water or at a high dry temperature before hot dipping;

In order to prevent the occurrence of pinhole leakage plating, it is usually to strengthen the technological measures, mainly to strengthen the pretreatment, regularly carry out the alloy solution purification treatment, and add the alloy elements.