Industrial problems stress-corrosion cracking

As an industrial problem stress corrosion cracking is of considerable importance. There is a long history of major and minor failures, particularly in the chemical industry and in the transport industry, particularly of components in ships and planes. It is a major potential source of failure in the nuclear power industry in which, for excunple, austenitic stainless steels may fail in high purity water containing oxygen and chloride ions at the level of ppb. 

Localized corrosion, which occurs when the anodic sites remain stationary, is a more serious industrial problem. Forms of localized corrosion include pitting, selective leaching (eg, dezincification), galvanic corrosion, crevice or underdeposit corrosion, intergranular corrosion, stress corrosion cracking, and microbiologicaHy influenced corrosion. Another form of corrosion, which caimot be accurately categorized as either uniform or localized, is erosion corrosion. 

In accordance with these definitions, stress-corrosion cracking has been a familiar problem in the petroleum and chemical industries for decades. Consequently, measures seem to be rather well established and generally known for preventing stress-corrosion cracking or for keeping it in check. Where conditions are such that this type of hydrogen attack can be expected, appropriate supplemental requirements should be included in the specification. A vessel built only to code requirements could be rendered unserviceable in a matter of hours by stress-corrosion cracking. 

The residual stress in a metal, or more commonly an alloy, wiU, in certain corrosive environments, result in mechanical failure by cracking. It first became apparent at the end of the nineteenth century in brass (but not copper) condenser tubing used in the electric power generating industry. It was then called season cracking. It is usually prevalent in cold-drawn or cold-roUed alloys which have residual stress. Heat treatments to relieve this stress were developed to solve the problem. It was soon realized that there were three important elements of the phenomenon the mechanical, electrochemical, and metallurgical aspects. 

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