Investigating the effect of surface quality of Rhodium electroplating coatings on their electrochemical and corrosion propertices

this research focused on investigating the optimization and corrosion studies of rhodium plating coatings. Firstly, a rhodium coating was applied to the Inconel 600 super alloy substrate for 2, 5, 10, 20 and 50 minutes, using the electroplating process of sulfate solution. Using scanning electron microscope (SEM) and X-ray energy spectroscopy (EDS) images, the thickness, morphology and elemental analysis of the surface coatings were investigated and effect of rhodium plating time on the thickness and surface roughness of the coating was investigated. Finally, the corrosion resistance of rhodium coatings in 3.5%wt NaCl solution was evaluated using electrochemical tests: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and tafel polarization, respectively. The results of SEM and roughness measurement studies in comparison results of rhodium coating showed that the electroplated rhodium coating had the highest resistance to electrochemical corrosion in 10 minutes, the thickness of the coating was 1.27μm and the corrosion current was 6.25nA/cm2 and the corrosion potential was determined to be 193mV vs SCE. the changes in the surface roughness were similar to the results of fitting the simulated electrical equivalent circuit for the double layer capacitance of the electrochemical impedance test.