双极电化学清除钛合金表面铁污染

Dipolar Electrochemical Removal of Iron Contamination on Titanium Alloy Surface

目的 针对耐蚀合金表面洁整化制造中,清洗介质和零件形状对清除表面异质铁污染的重要影响,提出了一种采用双极电化学清除铁污染的方法。方法 采用COMSOL软件建立双极电化学模型,仿真计算了不同驱动电位和样品位置对表面电位分布及清除速率的影响,对喷丸强化后的钛合金表面进行铁污染清除试验,利用邻菲罗啉显色检验和电化学阻抗验证铁清除效果,分析典型参数对铁污染清除效果的影响。结果 仿真模拟中电解池内的电压呈对称分布,样品表面电位为0 V;样品位于电解池中近正极1/4处时,其清除速率较中间位置时低;随驱动电压增加,有效清除长度减小,清除速率下降;显色检测显示钛合金原始试样表面的铁污染程度不均匀,红色色度值最高为15.5,清洗后合金表面从红色变为无色,阻抗谱图显示合金表面的耐蚀性增加。结论 试验与仿真模拟结果吻合良好,双极电化学可用于钛合金表面铁污染的清除,为钛合金表面高清洁度制造提供了一种新思路。

Aiming at the important influence of cleaning medium and part shape on the removal of surface heterogeneous iron contamination in the clean and tidy manufacturing of corrosion-resistant alloy surfaces, a method for removing iron contamination by bipolar electrochemistry was proposed. Firstly, the electrochemical module in COMSOL software was used to establish the bipolar electrochemical model. The size of the electrolytic cell was 20 cm×10 cm, the size of the cleaning sample was 6 cm×0.2 cm, and the cleaning solution was the mixed solution of 3 mol/L NaSOand 0.2 mol/L NaHPO. The potential distribution of electrolytic cell under different driving voltages(2 V, 6 V, 10 V, 30 V, 60 V) was calculated. The potential distribution changes in the cell were calculated when the sample was located in the middle of the cell and near the positive 1/4 when the driving voltage was 10 V. The potential data fitted with the potential distribution curve in the clearance solution 3 mm away from the lower surface of the sample. Secondly, a standard three-electrode system was used to measure the polarization curve of pure iron in the scavenging solution, in which a reference electrode was Ag/AgCl electrode and an auxiliary electrode was platinum electrode. The corrosion depth index was used to characterize the removal rate of iron pollution, and the removal rate curves under different parameters were drawn. Finally, iron pollution removal test was carried out on the surface of titanium alloy after shot peening. A 10 cm×15 cm platinum plate was used as the driving electrode, and the dc power supply was used.The removal effect was tested by the phenanthroline color reaction. In addition, the dynamic potential polarization scan and impedance-frequency scan were performed on the sample test surface before and after cleaning. This is used to analyze the corrosion resistance of the samples in general conditions before and after cleaning. The electrolyte was 3.5% NaCl, the scanning rate was 0.5 mV/s, and the scanning range was from-0.5 V to 1.5 V(relative to Ag/AgCl electrode). The results show that the voltage in the electrolytic cell is symmetrically distributed in the simulation, and the surface potential of the sample is 0 V. The removal rate of the sample in the middle of the electrolytic cell is higher than that near the positive electrode 1/4. With the increase of driving voltage, the effective removal length decreases, and the removal rate increases when the driving voltage exceeds 10 V. The color test shows that the iron contamination on the surface of the original titanium alloy sample is uneven,and the highest red chromaticity value was 15.5. After cleaning, the alloy surface changes from red to colorless, and the impedance spectroscopy shows that the corrosion resistance of the alloy surface increased. The experimental results are in good agreement with the simulation results. The bipolar electrochemistry can be used to remove the iron contamination on the surface of titanium alloy, which provides a new idea for high cleanliness manufacturing of titanium alloy surface.