Characterization and Corrosion Behaviour of Zn-Sn Binary Alloy Coatings in 0.5 M H2SO4 Solution

Abstract

This work examines the characterization and corrosion behaviour of laser alloyed UNSG10150 steel with three different premixed composition Zn-Sn binary powders using a 4.4 kW continuous wave (CW) Rofin Sinar Nd: YAG laser processing system. The steel alloyed samples were cut to corrosion coupons, immersed in sulphuric acid (0.5 M H2SO4) solution at 30°C using electrochemical technique and investigated for its corrosion behaviour. The morphologies and microstructures of the developed coated and uncoated samples were characterized by Optic Nikon Optical microscope (OPM) and scanning electron microscope (SEM/EDS). Moreover, X-ray diffractometer (XRD) was used to identify the phases present. An enhancement of 2.7-times the hardness of the steel substrate was achieved in sample A1 which may be attributed to the fine microstructure, dislocations and the high degree of saturation of solid solution brought by the high scanning speed. At scanning speed of 0.8 m/min, sample A1 exhibited the highest polarization resistance Rp (1081678ωcm2), lowest corrosion current density icorr (4.81×10-8 A/cm2), and lowest corrosion rate Cr (0.0005 mm/year) in 0.5M H2SO4. The polarization resistance Rp (1081678ωcm2) is 67,813-times the polarization of the UNSG10150 substrate and 99.9972% reduction in the corrosion rate.