Development of Bath Chemical Composition for Batch Hot-Dip Galvanizing—A Review

Abstract

Obtaining zinc coatings by the batch hot-dip galvanizing process currently represents one of the most effective and economical methods of protecting steel products and structures against corrosion. The batch hot-dip galvanizing process has been used for over 150 years, but for several decades, there has been a dynamic development of this technology, the purpose of which is to improve the efficiency of zinc use and reduce its consumption and improve the quality of the coating. The appropriate selection of the chemical composition of the galvanizing bath enables us to control the reactivity of steel, improve the drainage of liquid zinc from the product surface, and reduce the amount of waste, which directly affects the quality of the coating and the technology of the galvanizing process. For this purpose, the effect of many alloying additives to the zinc bath on the structure and thickness of the coating was tested. The article reviews the influence of various elements introduced into the bath individually and in different configurations, discusses the positive and negative effects of their influence on the galvanizing process. The current development in the field of the chemical composition of galvanizing baths is also presented and the best-used solutions for the selection and management of the chemical composition of the bath are indicated.

The Impact of Heat Treatment on the Behavior of a Hot-Dip Zinc Coating Applied to Steel During Dry Friction

“…On the other hand, the δ phase layer is thicker and compact. The next phase, ζ, shows two distinct zones [ 19 ]. The inner layer, formed by reactive diffusion between Fe and Zn, has a stable thickness and compact structure.…”

“…In fact, the microstructure of the hot-dip zinc coating can differ significantly from that in the model. Such factors as the method of preparation of the galvanized surface [ 11 , 12 , 13 , 14 , 15 ], the chemical composition of the base surface [ 16 , 17 , 18 ], the chemical composition of the zinc bath [ 19 , 20 , 21 , 22 , 23 , 24 ], the parameters of galvanization [ 25 , 26 , 27 , 28 , 29 ], etc., may cause microstructural differentiation even within the same coating ( Figure 1 b). Most of the mentioned parameters influence the reactivity of steel, and only the optimal selection of galvanizing conditions enables the formation of a proper zinc coating.…”

“…The reactivity of steel in the Sandelin range (steel with silicon) can be controlled by adding Ni. Control of the steel’s reactivity can be also achieved with the assistance of Al, Bi, and Sn [ 19 ]. The mechanical properties of the zinc coating are dependent on its microstructure and are consequences of the properties of the individual phases visible in the coating cross section.…”

Comparison of the Tribological Properties of the Thermal Diffusion Zinc Coating to the Classic and Heat Treated Hot-Dip Zinc Coatings

“…Pressure to reduce the production cost means that more and more often structural elements are made of less advanced materials that guarantee only the appropriate mechanical properties. Additional functional properties, such as corrosion resistance and wear resistance, are obtained by applying appropriate coatings, whose thicknesses vary over a wide range—from nanometers [ 7 ] to several hundred micrometers [ 8 ]. To increase the wear resistance, harder and harder coatings are applied, with a hardness up to 1700 HV [ 9 , 10 ].…”

Effect of Mg on the Formation of Periodic Layered Structure during Double Batch Hot Dip Process in Zn-Al Bath

“…However, the increasingly higher requirements for the corrosion resistance of steel products mean that the zinc coating often does not meet these expectations. Additionally, the widespread use of Pb [ 4 ], Bi [ 5 ] and Sn [ 6 ] alloying additions may lead to a reduction in their corrosion resistance [ 7 ]. Therefore, new zinc baths based on Zn-Al-Mg alloys for hot dip galvanizing have been developed.…”