Abstract
Stress corrosion cracking of line pipe from the soil side involves slow crack growth at stresses which may be as low as half the yield strength of the steel. The majority of failures experienced in various parts of the world are characterised by being associated with intergranular stress corrosion cracks, resulting from the presence of carbonate-bicarbonate solutions with pH’s of about 9.5. More recently transgranular cracks, due to the presence of carbon dioxide-containing solutions having pH’s in the vicinity of 6.5, have been observed. The emphasis in this paper is on approaches to prevention and control, making use of the controlling parameters identified by research into the problem. For existing lines, control of the problem may be through manipulation of the stressing conditions and, in principle, control of the cathodic protection, with temperature control offering an alternative approach for cracking by the higher pH environment but not that of low pH. For new lines, the additional factors of steel composition, surface condition and coating system and quality may be added to the above for control of the problem.
