Improvement of hot galvanizing coating by adding CdCl2, NiCl2 and SnCl2

Abstract

Hot-dip galvanization is a very common technique used worldwide to protect structural steels against corrosion. In this work we study effect of CdCl2, NiCl2 and SnCl2 on the morphology and on the structure of hot-dip galvanized coatings substrates used were hot-rolled sheets of AISI 1015 (St-37) steel. After sandblasting they were pickled (deoxidized) in an aqueous solution containing 10% HCl for about 20 min. When these salts were added in the preflux bath. From this investigation it turns out, that the morphology of the coatings formed after fluxing in a preflux bath containing CdCl2 is very similar to the morphology of the coatings formed in the usual flux. Sn addition seems to be inert with regard to the coating structure. This phenomenon is likely to be affected by the NiCl2 concentration but not by the solvent used (water containing 50% ZnCl2 .NH4Cl).