Environmentally Induced Cracking EIC

Cathodic protection, provided the material is not prone to embrittlement. Sacrificial zinc (galvanized) coatings may be used. 

Surface treatments such as hot peening, nitriding of steels, sandblasting of the surface of the metal and other treatments that produce constraints of compression are beneficial. 

Organic coatings, which can impede CF. The coatings must contain inhibitory pigments in the primary layer. Local defects in the coatings reduce the CF strength of carbon steel (9). 

Noble metal coatings, which are useful as long as they remain unbroken and are of high density and thickness. Electrolytic deposits of tin, lead, copper, silver, or steel are useful as protectors of CF (60). 

In some environments and under certain conditions, a microscopically brittle fracture of materials can occur at levels of mechanical stress that may be far below the level required for general yielding or those that cause significant damage in the absence of an environment. The susceptibility also depends on the chemical composition and microstructure of the alloy. This form of corrosion requires an interaction between the electrochemical dissolution of the metal, hydrogen absorption, and the mechanical loading conditions (stress, strain, and stain rate) (73). The nature of these fracture modes varies from one class of material to another. However, all fracture modes are largely similar to one another. 

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Corrosion also occurs as a result of the conjoint action of physical processes and chemical or electrochemical reactions (1 3). The specific manifestation of corrosion is deterrnined by the physical processes involved. Environmentally induced cracking (EIC) is the failure of a metal in a corrosive environment and under a mechanical stress. The observed cracking and subsequent failure would not occur from either the mechanical stress or the corrosive environment alone. Specific chemical agents cause particular metals to undergo EIC, and mechanical failure occurs below the normal strength (5aeld stress) of the metal. Examples are the failure of brasses in ammonia environments and stainless steels in chloride or caustic environments. 

Mechanisms of Environmentally Induced Cracking (EIC). Environmentally assisted cracking spans a wide range from brittle fracture to electrochemical process and the underlying mechanisms are complex. 

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