Surface characterization, mechanical properties and corrosion behaviour of ternary based Zn–ZnO–SiO2composite coating of mild steel

Abstract

Zinc coatings are obtained either from cyanide, non-cyanide alkaline or acid solutions. Because of the pollution and high cost associated with cyanide, deposition from other baths is gaining importance. In order to develop a bath with additive that could produce a quality coating is the motivation behind this present work which is surface modification of Zn–8ZnO–SiO2 nano composite coating on mild steel surface by electrodeposition route. The influence of SiO2 on Zn–8ZnO sulphate electrolyte on the properties and microstructure of the produced nano-coatings were investigated. The SiO2 was varied from 0 to 16wt%. The microstructure characteristics of these produced series composites coating were investigated using scanning electron microscopy couple with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction and atomic force microscopy (AFM). The corrosion degradation properties in 3.65% NaCl medium were studied using potentiodynamic polarization technique and characterized by high resolution optical microscope (HR-OPM). The hardness and wear of the composite coating were measured with high diamond microhardness tester and dry abrasive MTR-300 testers respectively. The results showed that average hardness value of 142.5 and 251.2HV and corrosion rate of 0.13088 and 0.00122 mm/yr were obtained for the 0 and 16wt% SiO2 in Zn–8ZnO. The work have established that upto 16% SiO2 in Zn–8ZnO composite coating on mild steel can be used in improving the microhardness, wear loss and corrosion resistance of mild steel.