The influence of hot dip galvanizing process on intermetallic phases formation

Abstract

Cheaper metallic materials are susceptible to environmental corrosion due to low values of electrochemical potentials. For instance, low carbon steels, but recently ductile cast irons too, show many problems of mechanical properties degradation due to corrosion. Therefore, it is important to protect these alloys against corrosion for safety reasons by using low‐cost coating techniques like Hot Dip Galvanizing (HDG).

Utilization of Galvanizing Flue Dust Residue: A Sustainable Approach towards Complete Material Recycling

“…Accounting for over 50% is its use as a corrosion protection coating for steel. Globally, zinc is used to coat up to 95% of steel products, providing corrosion protection [1][2][3].…”

“…The technological process of hot-dip galvanizing utilizes immersion of a steel component in molten zinc at 450-470 • C. The galvanizing itself is preceded by the surface pre-treatment of the steel. Surface preparation is an important step, which begins with degreasing, followed by pickling and immersion in flux, with the aim of removing fats, oils, metal oxides, and other contaminants from the steel surface [2,16,17].…”

“…As a flux in dry hot-dip galvanizing, an aqueous solution of ZnCl 2 :2NH 4 Cl salts is applied, most often in a 1:2 ratio. The zinc coating is formed by a mutual reaction between molten zinc and steel to form the zinc-iron alloy phase [2,16,17].…”

“…When a steel component is immersed in the zinc bath, violent reactions occur where particles evaporate in the form of white fumes, which are collected on the filters, producing GFD waste. It is a product of zinc chloride and ammonium chloride decomposition contained in the fluxes [2,[16][17][18].…”

Intermetallic phase kinetic formation and thermal crack development in galvanized DCI

“…The main element that is usually considered as Pb substitute is the Sn, but other metallic elements can be used leading to different intermetallic phases formations and different corrosion and mechanical performances. More studies, oriented to the intermetallic phases damage, have been carried out [15][16][17][18] in order to better understand the behaviour of the intermetallic phases in tensile and in compression loads. In the last years a new cheap class of cast irons, the Ductile Cast Irons (DCIs) became more and more interested in galvanizing protection [19].…”