Development of the Iron Elimination Technology of Acid Cleaning Solution of Hot Dip Galvanizing Process

Abstract

Hot dip galvanizing is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other fields etc.. Recently, the cost of zinc is getting higher and higher, thus, a proper manufacturing process should be developed possibly to reduce the cost of production. one of hot dip galvanizing process, that is, acid cleaning process is very important to control more effective coating. However, acid solution is deteriorated with increasing its using time because dissolved iron from structural steel due to continuous acid cleaning was increasingly increased, and which is resulted in coating badness and increment of dross. In this study, elimination of iron dissolved in acid solution was investigated with some types of inner solution added with additives such as seawater, NH4OH, NaOH, NH4Cl and thiourea, and electrolysis experiment was carried out with parameters of applied current density. For elimination of iron from acid cleaning solution through electrolysis, it is considered that inner barrel with separator should be filled with solution different from original acid cleaning solution which is involved in iron ion, that is , the inner solution which is made up seawater added with additives such as NH4OH(10g) , NaOH(3.5g) and thiourea(0.5g) is the most desirable solution to effectively extract iron from acid cleaning solution. An optimum applied current density for the most extraction effect of iron through electrolysis experiment is thought to be 50mA/cm2 .