Effectiveness of Si contents in the steel composition on the corrosion performance of galvanized steel

Abstract

PurposeThe purpose of this work was to investigate the effect of Si content of steel substrate on the performance of the hot-dip galvanized layer. Moreover, the structure of the galvanized layers and the corrosion performance of the galvanized steel in 3.5 per cent NaCl solution have been studied.Design/methodology/approachThe galvanized layer has been formed by the hot-dip technique, and the influence of silicon content in the steel composition on the corrosion performance of the galvanized steel was estimated. The surface morphologies and chemical compositions of the coated layers were assessed using scanning electron microscopy and energy-dispersive X-ray analysis, respectively. Potentiodynamic polarization Tafel lines and electrochemical impedance spectroscopy (EIS) tests were used to evaluate the corrosion resistance of the galvanized steel in 3.5 per cent NaCl solution.FindingsThe results proved that adhere, compact and continuous coatings were formed with steel containing 0.56 Wt.% Si, while cracks and overly thick coatings were obtained with steel containing 1.46 Wt.% Si. Tafel plots illustrated that the corrosion rate of galvanized steel containing 0.08 and 0.56 Wt.% Si was lower than that of the galvanized steel containing 1.46 Wt.% Si. Also, the results of the EIS reveal that the impedance of the galvanized steel containing 0.08 and 0.56 Wt.% Si was the highest and the lowest, respectively, with the steel containing 1.46 Wt.% Si.Social implicationsGenerally, in industry steels containing high amounts of silicon (0.15-0.25 Wt.%) can be galvanized satisfactory either by controlling the temperature (440°C) or adding Ni to the galvanized bath. The low temperature reduces the coating thickness; nickel amount must be controlled to prevent the formation of higher amounts of dross. This study proved that high Si steel of up to 0.56 Wt.% can be galvanized at 460°C without adding Ni to the galvanized bath and form adhere, compact, free cracks and have good corrosion resistance. Consequently, a social benefit can be associated with galvanizing high Si steel, leading to an increase in the cost of the process.Originality/valueThe results presented in this work are an insight into understanding the hot-dip galvanizing of high Si steel. The corrosion resistance of galvanized steel containing 0.56 Wt.% Si alloys has been considered as a promising behavior. In this work, a consistent assessment of the results was achieved on the laboratory scale.