from the conferences organized by TANGER Ltd.
The existing knowledge on the use of alloying additives in the zinc bath was analyzed. The appropriate content of alloying additives in the bath affects the quality of the coatings and also optimizes the consumption of zinc. Al and Ni are currently used as standard bath alloying additives. Zinc baths also contain Pb, Bi and Sn, interchangeably used, as standard. These metals improve the fluidity of liquid zinc, which results in a beneficial reduction of zinc consumption and improves the appearance of the coating. However, the presence of Pb in the bath should be limited due to its toxicity, while Bi and Sn increase the risk of liquid metal embrittlement (LME). These metals can also contribute to lowering the corrosion resistance of coatings. An alternative to the currently used baths containing Pb, Bi or Sn can be a bath containing only the addition of AlNi. The article specifies the optimal concentration of Al and Ni addition for the bath. The synergistic effect of AlNi addition on the kinetics of coatings growth in the temperature range of 440-460 °C was determined. The microstructure was disclosed and the chemical composition in the micro-areas of the coatings on low-silicon steel and on steel from the Sandelin range was determined. It was found that the synergistic effect of the optimal AlNi additive content allows to obtain coatings with the correct appearance and thickness meeting the requirements of EN ISO 1461. The AlNi content effectively reduces the reactivity of Sandelin’s steel. The coatings obtained in the bath containing only the AlNi additive have a similar structure and thickness to the coatings obtained in the alternative baths containing Pb, Bi or Sn.
Keywords: Hot-dip galvanizing, zinc coatings, alloying additives© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.