Benefits and Limitations of the Use of Pb, Sn and Bi Alloying Elements in Hot Dip Galvanizing Bath: A Review

Abstract

Today, lead, bismuth and tin constitute the main group of alloying elements for zinc baths used for hot dip galvanizing. These metals improve the fluidity of liquid zinc, which positively affects the consumption of zinc and improves the appearance of the coating. However, their presence in the bath, despite their beneficial effects, is controversial due to the increased risk of liquid metal-assisted cracking (LMAC). Recent studies also indicate that these additives may contribute to lowering the corrosion resistance of coatings. The article analyzes the existing knowledge on the addition of lead, tin and bismuth to the bath and presents the benefits and limitations of using them as an alloying additive to the hot dip galvanizing bath.

Evaluation of Effect of Ti Addition to Zinc Bath on Kinetics of Growth of Alloy Layer Formed in Process of Hot-Dip Galvanisation on Steel Substrate

“…They inhibit the growth of intermetallic phases, modify the resulting phases, or alter corrosion properties, for example, by modifying the eta phase. Zinc bath additives affect not only the resulting coatings but also the conduct of the process by changing the physical properties of the liquid metal [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ].…”

“…Tin is an element that improves the viscosity of metal and reduces the surface tension of such a bath; it has a beneficial effect on Zn consumption in the process, and the resulting coatings are characterised by a more aesthetic, smoother surface finish [ 6 ].…”

“…Bismuth was found to have a beneficial effect on the casting properties of such baths by reducing the surface tension of the drip. As a result, this has been shown to reduce Zn consumption in the process by reducing the thickness of the η phase layer [ 6 , 10 ].…”