Effect of current density on microstructure and corrosion behavior of Co-P-nano-Al2O3 composite coating

In this study, Co-P-nanoAl2O3 composite coating was deposited onto AISI 430 substrate using direct current electric deposition technique. The microstructure and corrosion behavior of the fabricated coatings at different current densities (10 mA/cm2, 15 mA/cm2, 20 mA/cm2, 25 mA/cm2) were studied. In order to investigate the morphology of the composite coating and the analysis of the coated samples, scanning electron microscope (SEM) and EDS were used, respectively. The results showed, the composite coating formed at the current density of 15 mA/cm2, is completely uniform and continuous. In order to investigate the corrosion resistance, potentiodynamic polarization experiment was applied in aqueous solution of 3.5% NaCl on coated and uncoated AISI 430 samples. The results of Tafel and electrochemical polarization tests were also correlated with microscopic images and showed that the coated specimen at the current density of 15 mA/cm2 had the maximum corrosion resistance.