12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet - GALVATECH 2021

Currently, the optimum aluminum content in the alloy for Aluminum-zinc coating considered wt.55%. In addition to aluminum and zinc, the alloy contains 1.6 wt.% Silicon, which is introduced to suppress the exothermic reaction of the melt with iron. Cold-rolled steel coils with such a coating, has gained wide popularity and produced in many countries of the world. A coating with 55% aluminum has high corrosion resistance, and its production allows replacing zinc with aluminum and thereby reduces the specific gravity of the coating material, leading to savings of up to 75% zinc. However, the production of aluminum-zinc coating is associated with a large number of difficulties associated with the aggressiveness of the aluminum-zinc alloy with respect to the steel strip and the material of the pot equipment. As a result, a large amount of dross is formed, including the lower dross, which must be removed during each replacement of pot equipment. Compared to hot dip galvanizing, the campaign time for pot equipment is drastically reduced by 2–3 times. The plastic properties of the coating on the strip also deteriorate due to the thick intermetallic coating layer. This paper presents laboratory studies of the aggressiveness of alloys with different aluminum contents (from 5 to 55%) to steel base and materials of pot equipment. Based on the studies of the chemical activity of alloys with different aluminum contents, as well as metallographic and corrosion studies obtained coatings, the optimal composition of aluminum-zinc alloy for coating a steel strip was selected. The coating of the optimal composition has a corrosion resistance comparable to 55% Aluminum-Zinc Coating, also can significantly reduce the cost of the coating material compared to hot dip galvanizing, and its production is free from the inherent drawbacks of 55% Aluminum-Zinc Coating - the formation of lower dross and short life of pot equipment.