Stress corrosion cracking - O-ryoku fusokuware

This refers to the phenomenon in which metallic materials break under tensile stress in a specific corrosive environment. For example, aluminum alloys and austenitic stainless steels suffer from stress corrosion cracking in chloride aqueous solutions, and mild steel in alkaline aqueous solutions. The latter is also known as alkaline embrittlement. Stress corrosion cracking of copper alloys in ammonia is also known as season cracking. There are two types of cracking: intergranular cracking, which occurs along the grain boundaries, and transgranular cracking, which penetrates the grains. There are many unknowns about the mechanism of cracking,
(1) Repeated cracking and stress concentration due to selective corrosion.
(2) Stress-accelerated electrochemical corrosion,
(3) Acceleration of corrosion due to destruction of protective coatings on the surface caused by stress.
(4) Wedge effect of corrosion products
(5) Acceleration of corrosion due to stress-induced precipitation and transformation of different phases.
(6) Theories based on the theory of displacement, etc.
Many theories have been put forward, but there is no theory that can explain everything consistently, and it is doubtful whether it is a single phenomenon. It is often confused with hydrogen embrittlement, which is caused by the absorption of hydrogen that occurs during corrosion.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

金属材料が引張応力のもとで，特定の腐食環境下で破断する現象をいう．たとえば，アルミニウム合金，オーステナイト系ステンレス鋼は塩化物水溶液中で，また軟鋼はアルカリ水溶液中で応力腐食割れを起こす．後者はアルカリ脆性ともよばれる．アンモニア中での銅合金の応力腐食割れはseason crackingともよばれる．割れの形態としては，結晶粒界に沿って割れる粒界割れと，結晶粒を貫通する貫粒割れとがある．割れの機構については未知の点が多く，
(1)選択腐食による割れの発生と応力集中の繰り返し，
(2)応力により加速された電気化学的腐食，
(3)応力による表面保護皮膜の破壊による腐食の促進，
(4)腐食生成物のくさび効果，
(5)応力による異相の析出や変態による腐食の促進，
(6)転位論にもとづく説など，
多くの説が提出されているが，すべてを矛盾なく説明できる理論はまだなく，また，単一な現象であるかどうか疑わしい．腐食に伴い発生する水素の吸蔵による水素脆化と混同されることが多い．

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