微量Cl~-对316L不锈钢在沸腾乙酸—甲酸混合介质中的腐蚀行为的影响

通过腐蚀失重测量、极化曲线测试和AES分析,研究了微量Cl~-对316L不锈钢在沸腾的84％乙酸—10％甲酸—6％水中的腐蚀行为的影响。结果表明,微量Cl~-(50ppm)的吸附对316L的活性溶解有抑制作用。Cl~-浓度再高则腐蚀速度增大。316L在阳极极化时呈现钝化行为,阳极钝化膜富铬、贫铁,Cl~-使钝化膜的铬、铁含量降低,铬/铁比也降低,从而氧/(铬+铁)比升高,膜的保护性能降低,一定条件下可诱发孔蚀。常温下恒电位阳极极化使Cl~-在表面吸附并进入钝化膜内,温度升高则吸附作用减弱。

EFFECT OF TRACE Cl~- ON CORROSION BEHAVIOR OF 316L SS IN BOILING ACETIC ACIDFORMIC ACID MIXTURE

Effect of trace Cl~- on corrosion behavior of 316L SS in boiling 84％ acetic acid-10% formic acid-6％ water mixture is investigated by weight loss, polarization measurement and AES tests. Trace Cl~-(50ppm) has a slight inhibition effect on the anodic dissolution of the material because of its adsorption on the surface, but corrosion rate increases when the concentration of Cl~- increases to 200 ppm. Anodic passivation region is found on the anodic polarization curve and the passive film formed on the surface is enriched in Cr and O but depleted in Fe and Ni. The addition of Cl~- decreases the content of Cr and the Cr/Fe ratio in the film, and thus increases the O/(Cr+Fe) ratio. Then the protective effect of the passive film decreases and pitting incurs.