目的 通过调节电流密度的方法,提高316L不锈钢表面质量的同时获得较高耐蚀性。方法 由316L不锈钢极化曲线设置不同电流密度下电解抛光的实验组,通过3D激光显微镜扫描仪、电子显微镜（SEM）、能谱分析仪（EDS）和电化学工作站等设备,研究不同实验组的表面质量水平和腐蚀钝化行为,探索不同电解抛光电流密度对316L不锈钢腐蚀规律。结果 当电流密度为4 mA/cm2时,不锈钢表面粗糙度为0.229 μm,达到实验组最小值,划痕显著减少,麻点数量急剧下降,表面平整度与轻微腐蚀痕迹并存,呈现最佳表面质量;在电流密度为4 mA/cm2时,其腐蚀电位达到了最大值0.203 V,腐蚀电流降低至1.043 µA/cm2,腐蚀速率也随之降低至0.012 mm/a。电解抛光产物扩散速度较为合适,能够在不锈钢表面形成覆盖性较好的钝化膜,具有更好的防护性能,不易遭受腐蚀介质的侵蚀,耐腐蚀性提高。结论 316L不锈钢电解抛光的电流密度可参考其预实验对比组的极化曲线,在稳定钝化区内选择,可得到表面质量以及耐腐蚀性能较好的电流密度。在实验组中,316L不锈钢电解抛光后的表面质量水平以及耐腐蚀性能在钝化区电流密度为4 mA/cm2时达到综合最佳水平。
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.
关键词
316L不锈钢 /
电解抛光 /
电流密度 /
表面质量 /
耐腐蚀性 /
钝化膜
Key words
316L stainless steel /
electropolishing /
current density /
surface quality /
corrosion resistance /
passivation film
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基金
横向项目（W2024JSKF0081）; 安徽省省级大学生创新创业训练计划项目（S202410359374）
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