11611 Prevention of SCC

A simple approach to avoiding SCC can be deduced from Fig. 11.11, where SCC results from an appropriate combination of material type, environment, and stress. SCC can therefore be reduced or eliminated by: (i) removing or reducing the working or residual stresses within the component or inducing compressive residual stresses, (ii) controlling the environment, that is, composition, temperature,

pH, and potential, applying anodic or cathodic protection, and (iii) changing alloy composition or structure.

A reduction in the stress can have a significant effect on SCC if the cracking is caused by residual stresses, for example, a simple annealing treatment can be carried out. Furthermore prevention of mechanical damage, that is, hammering/machining, can elevate susceptibility. Environmental control is not always possible particularly when side reactions occur as a result of slight changes in process variables. However, if SCC occurs outside a set of well-known electrochemical parameters, that is, pH, temperature, concentration, and metal potential, careful monitoring and control of the environment can avoid possible cracking.

Material selection is perhaps the easiest of all the options available for an engineer and although corrosion-resistant materials are more expensive, it is often more economical, based on full life-cycle costs, to use such materials.

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