Influence of Current Density on Electrochemical Polishing and Corrosion Behavior of 316L Stainless Steel

XIA Jiazhen; LI Xin; HUA Lin; ZHAO Wanyi; PAN Gang; CHEN Wenjuan

doi:10.16490/j.cnki.issn.1001-3660.2025.24.013

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Surface Technology ›› 2025, Vol. 54 ›› Issue (24) : 163-172. DOI: 10.16490/j.cnki.issn.1001-3660.2025.24.013

Corrosion and Protection

Influence of Current Density on Electrochemical Polishing and Corrosion Behavior of 316L Stainless Steel

XIA Jiazhen, LI Xin, HUA Lin, ZHAO Wanyi, PAN Gang, CHEN Wenjuan^*

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Abstract

It is an advanced surface treatment technology by adjusting the electropolishing current density to improve the properties of 316L stainless steel, such as surface quality, corrosion resistance, and wear resistance. As the current density exerts a significant influence on the electropolishing of 316L stainless steel, it becomes a crucial factor in regulating the electropolishing process for this material. This study aims to enhance the surface quality of 316L stainless steel and achieve higher corrosion resistance by adjusting the electropolishing current density.
An electrochemical polishing study was conducted with 316L stainless steel as the anode and a copper sheet as the cathode, at an anode-to-cathode area ratio of 3∶1. The electrolyte was a mixture of concentrated sulfuric acid (98vol.%) and concentrated phosphoric acid (98vol.%) in a volume ratio of 3∶7. The 316L stainless steel samples were ground and cleaned prior to treatment. Based on potentiodynamic polarization curve test results from pre-experimental comparison groups, which provided reference current densities for the transition region, the stable passivation region, and the transpassive region, appropriate current densities were set for electrochemical polishing. Analysis of the experimental results involved: observation and analysis of the surface morphology and elemental distribution of the polished samples with a Regulus8100 scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS) at a magnification of 800X; examination of the surface morphology of the polished 316L stainless steel with a VK-X250 3D laser measuring microscope; and evaluation of the electrochemical behavior of the samples with a CS310 electrochemical workstation. The electrochemical impedance spectroscopy (EIS) tests employed a sinusoidal signal with a frequency range of 10^-2 to 10⁵ Hz and an amplitude of ±10 mV. Potentiodynamic polarization tests were performed in a scanning range of -0.3 to 0.3 V (vs. open circuit potential, OCP) at a scan rate of 0.2 mV/s. Test data was fitted and analyzed by Origin software. The corrosion test solution was CASS (Copper-Accelerated Salt Spray) solution, consisting of 50 g/L sodium chloride (NaCl) and 0.26 g/L copper (Ⅱ) chloride dihydrate (CuCl₂·2H₂O), with glacial acetic acid (CH₃COOH) added to adjust the pH to 3.1-3.3. The surface quality and corrosion resistance of the 316L stainless steel after electrochemical polishing at different current densities were analyzed.
The optimal current density for electrochemical polishing of 316L stainless steel should be selected within the stable passivation region of its potentiodynamic polarization curves, as determined through pre-experimental comparative groups. This approach yields enhanced surface quality and corrosion resistance. Among the experimental conditions, a current density of 4 mA/cm² in the passivation region delivered optimal overall performance for both surface integrity and corrosion resistance. At a current density of 4 mA/cm², the stainless steel surface roughness reached its minimum value of 0.229 µm within the experimental groups. Scratches were significantly reduced, the number of pits decreased sharply, and the surface exhibited optimal quality characterized by high flatness coexisting with slight etching traces. Furthermore, at 4 mA/cm², the corrosion potential reached its maximum value of 0.203 V, while the corrosion current density decreased to 1.043 µA/cm² and the corrosion rate reduced to 0.012 mm/a. This indicates that the diffusion rate of the electrochemical polishing products is appropriate, enabling the formation of a passive film with relatively good coverage on the stainless steel surface. This film provides enhanced protective properties, making the surface less susceptible to attack by corrosive media and consequently improving the corrosion resistance.

Key words

316L stainless steel / electropolishing / current density / surface quality / corrosion resistance / passivation film

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XIA Jiazhen, LI Xin, HUA Lin, ZHAO Wanyi, PAN Gang, CHEN Wenjuan. Influence of Current Density on Electrochemical Polishing and Corrosion Behavior of 316L Stainless Steel[J]. Surface Technology. 2025, 54(24): 163-172

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