18Cr-8Ni オーステナイト系ステンレス鋼の応力腐食割れにおよぼす腐食雰囲気中の酸素の影響について(性質関係)

概要

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In order to study the behavior of oxygen dissolved in corrosives which has been reported to influence the stress corrosion cracking of austenitic stainless steels, the specimens of the steel were stressed and exposed to 42% MgCl_2 solution or 40% FeCl_2 solution under nitrogen or normal atmosphere, and the change in ductility and hardness during corrosion, and fracture time were measured. The results obtained are summarized as follows : (1) In 42% MgCl_2 solution without dissolved oxygen, the stress corrosion cracking occurred both in case of whole immersion specimen or half immersion specimen. (2) It was concluded that the dissolved oxygen is necessary for pitting to occur in high temperature sodium chloride solution, but, after the initial pit forms, the crack propargation may depend on hydrogen embrittlement which is resulted from the phenomenon that low pH FeCl_2 is filled in the pit by electrochemical reaction. (3) The stress corrosion mechanism seemed to be illustrated from the standpoint of crevice corrosion mechanism, and consequently it was concluded that not oxygen but hydrogen plays an important role in stress corrosion cracking processes.
社団法人日本鉄鋼協会の論文
1970-02-01