不锈钢在不同介质中的正负交变电脉冲处理及其对耐腐蚀性的影响

Anodic/Cathodic Electrical Pulse Treatment of Stainless Steel in Various Mediums and Its Influence on Corrosion Resistance

电化学诱导退火(EIA)是一种通过对不锈钢进行正负交变电脉冲处理提高不锈钢的耐蚀性的方法,但是其所用介质亚硝酸钠是一种强的致癌物质,且单一的处理介质限制了该方法的工业应用。本工作在不同介质中对不锈钢进行了正负交变电脉冲处理,通过XRD测试、金相观察、循环伏安测试、极化曲线测试等方法研究处理前后的组织变化、耐腐蚀性变化及其机理。结果表明,EIA相变可以在亚硝酸钠以外的介质,如碳酸钠溶液中实现,氮不是发生EIA相变的必要条件;适当延长电脉冲处理的阴极部分时间能够提高1mol/L碳酸钠溶液中的EIA处理效率。碳酸钠中的EIA相变也可以降低不锈钢在NaCl水溶液中的点蚀敏感性;在亚硫酸钠、硅酸钠和乙酸钠溶液中的电脉冲处理易导致马氏体被优先腐蚀。

Electrochemically induced annealing （EIA） is a method to improve the corrosion resistance of stainless steel with a series of anodic/cathodic electrical pulses. However, the treatment solution of sodium nitrite is a kind of carcinogen, and the only medium confines the industrial application of the treatment. Stainless steel samples were treated in several solutions with a series of anodic/cathodic electrical pulses in the present work. The changes of the corrosion resistance and surface microscopic structure of the steel after the treatment and the mechanisms were studied with XRD, metallographic observation, cyclic voltammetry test and potentio dynamic scanning. Results showed that EIA phase transformation could occur in mediums other than sodium nitrite, such as sodium carbonate. Nitrogen is not an essential condition for the EIA phase transformation. Efficiency of the treatment in 1 mol/L sodium carbonate solution could be improved by reasonable prolonging the cathodic intervals of the electrical pulses. Pitting sensitivity of the sled in sodium chloride solution could also be reduced with the EIA treatment in the sodium carbonate solution. However, the electric pulse treatment in solutions of sodium sulfite, sodium silicate and sodium acetate caused preferential corrosion of the martensite in the steel.