Technical Note: Stress Corrosion Cracking in Pipe Steels: The Influences of Residual Impurities on Service Failures Available to Purchase

It is nearly three years since the publication of a correlation between grain boundary segregation of impurity elements in low carbon steels with their susceptibility to dissolution controlled intergranular stress corrosion cracking (IGSCC).¹  This correlation was based on laboratory tests in nitrate solutions²  of a high purity 0.15% C steel in which ten common residual elements in commercial purity steels were added individually to the melt at bulk levels within ranges found in practice and low enough to have no significant effect on microstructure at any stage of the processing. During the processing heat treatments, these elements diffuse and accumulate at the grain boundaries with an enrichment at equilibrium of between 1 (no enrichment) and 10,000.³  For some elements, the enrichment may not be at equilibrium because of poor diffusion kinetics. When in service, the segregated impurities may or may not exacerbate the corrosive attack or the...