Evaluation of Temperature and Electrolyte Concentration in Electropolishing Process on Corrosion Resistance of Inconel 718 Alloy

Improvement of the corrosion resistance capability by the electropolishing (EP) is one of the most importance process surface modification. In this paper, the effects of two variables perchloric acid concentration and bath temperature on the electropolishing process and the corrosion resistance performance of the Inconel 718 alloy were studied. Evaluation of microstructure and surface roughness quality before and after electropolishing process by the scanning electron microscopy (SEM) and surface roughness test were used, respectively. In order to determine voltage range and current electropolishing to I-V curves were used. The results showed that, obtain to uniform surface and without pores can be achieved only under the conditions has the electrolyte composition as 10 vol% H2O -70 vol% CH3COOH -20 vol% HClO4 and bath temperature is 15 C. Electropolishing rate in the above conditions at the grain boundaries and inside the grains came close together and lead to a smooth and uniform surfaces. The minimum surface roughness after electropolishing on the above condition amount 0.026 ?m obtained. The results of the TOEFL polarization test in a solution of 0.5M H2SO4 + 0.01M KSCN indicated, electropolishing Inconel 718 alloy reduces the corrosion current density and become more Noble in potential (Ecorr). Electropolished samples under optimized conditions has exhibited the highest resistance to corrosion. The reason improving in the corrosion resistance Inconel 718 alloy by electropolishing that was attributed to the formation of very uniform oxide layer on surface and microstructure free of cavities.