高温碱液中NaClO_3杂质浓度对1Cr18Ni9Ti耐蚀性的影响

Effect of Concentration of Impurity NaClO_3,on Corrosion Resistance of 1Cr18Ni9Ti Stainless Steel in High-Temperature Caustic Solution

杂质对奥氏体不锈钢在高温碱液中的耐蚀性影响较大,其中以NaClO3杂质的影响最显著。通过动电位极化试验、浸泡试验、3点弯曲应力腐蚀试验并结合腐蚀产物的XRD和SEM分析,研究了1Cr18Ni9Ti不锈钢(18-8)在150℃,50%NaOH溶液中的耐蚀性。结果表明,18-8耐蚀性与高温碱液中NaClO3杂质的含量有关,随着NaClO3杂质浓度的提高,18-8的耐蚀性提高,其主要是溶液的氧化性增强,18-8表面形成了致密的保护膜;只有当溶液中NaClO3浓度为0.15%时,18-8才发生应力腐蚀开裂,这主要是表面膜层的保护性有限,此时应力腐蚀开裂符合阳极溶解机理。

By making use of potentiodynamic polariza-tion test,immersion test,and three-point bending stress corro-sion test,and in association with analysis of the corrosion prod-ucts by means of X-ray diffraction and scanning electron micros-copy,the corrosion resistance of 1Cr18Ni9Ti stainless steel in the aqueous solutions of 50wt% NaOH containing different content of NaClO3 impurity at 150 ℃ was studied.Results show that the corrosion resistance of the stainless steels in high temperature caustic solutions is closely related to the content of NaClO3 impu-rity in the heated caustic solution.The corrosion resistance of 1Cr18Ni9Ti increases with increasing content of NaClO3 in the so-lution,which is attributed to the formation of a protective film on the surface of the steel in the presence of NaClO3 as an oxidizing agent.When the concentration of NaClO3 impurity in the caustic solution reached 0.15%,the stainless steel was liable to stress corrosion cracking,due to inadequate protection of the protective film.And the mechanism of stress corrosion cracking of the stain-less steel can be explained using anode dissolution theory.