Overview of zinc melt alloying systems for hot dip galvanizing

Abstract

Hot dip galvanizing is one of the most common and effective methods for obtaining protective coatings on building structures and various products. This process has been used for more than 150 years, but the last decades have seen a dynamic development of this technology in order to reduce the consumption of zinc, as well as improve the quality of the coating. To date, many researchers have tested the effect of various alloying additions to the zinc bath on the structure and thickness of the coating. The article presents the studies of coatings obtained in baths with additives of aluminum, nickel, lead, bismuth, tin, vanadium, titanium, introduced into the galvanizing bath in various configurations. It has been given data on combinations of alloying additions, which make it possible to control the reactivity of steel with different silicon contents. It has been shown that the reactivity of Sandelin steel containing 0.03–0.12 % Si can be controlled by adding Ni or a combination of Ni + Bi. In addition, Al, Bi and Sn can help control the reactivity of the steel. The effect of additives on the quality of the coating surface is shown. The addition of Pb, Bi and Sn improves the flow of liquid zinc from the surface of the product. However, one should also take into account the negative consequences of their exposure, mainly the toxicity of lead and the possibility of increasing the risk of liquid metal embrittlement when using Bi and Sn. The positive and negative consequences of the influence of some additives on the process of formation of galvanizing waste are considered. Modern developments in the field of commercial zinc alloys for galvanizing baths are also presented. Optimal solutions for choosing a bath alloying system and recommendations for the limits of changing the concentration of each element are indicated.