目的 从镀层的耐蚀性能、电化学行为、镀液稳定性三个层面分析硫酸根对甲基磺酸体系镀锡的影响，探究在不影响镀液性能的条件下，硫酸根在甲基磺酸镀锡液中的最大浓度范围。方法 通过盐雾实验和电化学测试探究硫酸根对镀锡板耐蚀性能的影响，通过电化学测试研究了硫酸根在甲基磺酸镀锡过程中的电化学行为，通过可见光分光光度计和zeta电位仪分析硫酸根对镀液稳定性的影响。结果 镀液中硫酸根质量浓度在5 g/L时，镀层的耐蚀性能最好，但硫酸根质量浓度高于10 g/L时，镀层耐蚀性呈下降趋势。在锡沉积过程中，硫酸根离子的存在会增大锡沉积的阴极极化，当镀液中的硫酸根质量浓度达到60 g/L时，阴极极化不再显著增加。透过率随时间变化的曲线表明，当MSA和甲基磺酸混合溶液中不存在硫酸根时，溶液的氧化速度较慢，溶液透光率经过196 h后由99%下降为86%。硫酸根的加入会使镀液的氧化速率加快，当溶液中硫酸根质量浓度分别为20、40、60、80 g/L时，196 h后，透光率分别下降至15%、66%、63%、20%。硫酸根的加入，也会改变溶液的zeta电位，使胶粒由荷正电变为荷负电。结论 当镀液中硫酸根质量浓度超过10 g/L时，镀锡层的耐蚀性能下降。硫酸根能够增大锡沉积的阴极极化，加速锡离子的氧化；此外，硫酸根还会吸附在锡胶粒表面，使添加剂浊点降低。

The work aims to analyze the effects of sulfate on the tin plating of the sulfate-p-toluenesulfonic acid system from corrosion resistance and electrochemical behavior of plating and stability of plating solution and investigate the maximum con-centration range of sulfate in the methanesulfonic acid plating solution without affecting the performance of the plating solution. The effect of sulfate on the corrosion resistance of tinplate was investigated by salt spray experiments and electrochemical tests. The electrochemical behavior of sulfate in tin plating with methanesulfonic acid was studied by electrochemical tests and the visible light spectrophotometer and zeta potentiometer were used to analyze the effect of sulfate on stability of tin plating solution. From the test results, with the increase of the sulfate concentration in the bath, the corrosion resistance of the coating was the best at 5 g/L. When the concentration of sulfate was higher than 10 g/L, the sulfate concentration tended to decrease. During the deposition of tin, the sulfate ions increased the cathodic polarization of tin deposition. When the concentration of sulfate in the bath reached 60 g/L, the cathodic polarization curve did not increase significantly. From the curve of light transmittance over time, when there was no sulfate in the mixed solution of MSA and methanesulfonic acid, the oxidation rate of the solution was slow, and the solution light transmittance decreased from 99% to 86% after 196 h. The oxidation rate of bath could be accelerated when the concentration of sulfate in the solution was 20, 40, 60 and 80 g/L, respectively. After 196 h, the transmittance decreased to 15%, 66%, 63% and 20%. The addition of sulfate also changed the zeta potential of the solution and transformed the colloidal particles from positive charge to negative charge. When the concentration of sulfate in the plating solution exceeds 10 g/L, the corrosion resistance of the tin plating layer decreases. The sulfate radical can increase the cathodic polarization of tin deposition and accelerate the oxidation of tin ions. Moreover, sulfate radicals are adsorbed on tin colloid to reduce the cloud point of the additive.