Soils stress-corrosion cracking

Stress Corrosion Cracking One of the serious forms of pipeline corrosion is see. This form of corrosion consists of brittle fracture of a normally ductile metal by the conjoint action of a specific corrosive environment and a tensile stress. In the case of underground pipelines, see affects the external surface of the pipe, which is exposed to soil/ground water at locations where the coating is disbonded. 

F. M. Song, Predicting the effect of soil seasonal change on stress corrosion cracking susceptibOity of buried pipelines at high pH, Corrosion 66 (2010) 1—14. 

Determining susceptibility of a materitJ to stress corrosion cracking or hydrogen embrittlement in a soil environment has been studied using buried U-bend specimens [S]. 

Some specific corrosion environments, in the presence of applied tensile stress on the metal siuface (above some threshold vtilue), can cause stress-corrosion cracking (SCC). The somce of stresses can be extemtil, but residual stresses can tilso cause SCC failures. Specific corrosive pollutants, which may contribute to the SCC of carbon steels, are for example, the carbonates in water. Sulfide stress cracking (SSC) commonly occms on the outside of a pipe where sulfate-reducing bacteria me present at a soil pH of 3-7. Because of the produced iron sulfide (FeS), which adsorbs readily on the steel surface, hydrogen atoms generated... 

Asphalt/coal tar Easy to apply Minimal surface preparation required Long track record in certain environments without failure Permeable to cathodic protection in event of failure Subject to oxidation and cracking Soil stress has been an issue Limitations at low application temperatures Environmental and exposure concerns Associated with corrosion and stress crack corrosion failures... 

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