Effect of Cr Sulfate Concentration, Electrodeposition Temperature and Duration on Characteristics and Properties of Cr Coatings

Cr coatings were produced from chromium sulfate based solutions. Effect of chromium sulfate concentration, as well as electrodeposition temperature and duration on cathodic current efficiency, thickness, morphology, microstructure and microhardness of the resultant coatings were investigated. The results revealed that current efficiency increased from 16 to 27% with increasing the Cr sulfate concentration of the bath from 0.15 to 0.3 M. However, further enhancing the Cr sulfate concentration resulted in lower current efficiency. Variation of Cr sulfate concentration of the bath had negligible effect on microhardness of Cr films (923-930 Hv). Cathodic current efficiency, thickness and microhardness of the coatings were decreased by raising the temperature from 20 to 60°C. Increasing the deposition time from 10 to 180 min resulted in higher thicknesses, while current efficiency decreased from 33 to 10%. All of the coatings had amorphous structure. SEM micrographs showed that morphology of Cr coatings was lumpy containing micro-cracks. However, cracks density was decreased by increasing temperature or reducing deposition time

کلیدواژه ها:

Electrodeposition ، Cr coating ، Microhardness ، Current efficiency ، Deposition parameters