Study of Stress Corrosion Cracking of X70 Pipeline Steel in Near Neutral pH Solution

摘要

Stress corrosion cracking (SCC) of an X70 line pipe steel, in near neutral pH SCC solutions was studied. The microstructure of the X70 steel was characterized using high resolution transmission electron microscopy (TEM). The local electrochemistry under a disbonded coating was studied using a micro-electrode technique. The SCC of the X70 steel was studied using a slow strain rate test (SSRT) and ripple loading. The results showed that the precipitated hardening, dislocation hardening and grain size hardening would increase the SCC susceptibility of the X70 steel. Insufficient cathodic protection or shielding of the cathodic protection by a disbonded coating would cause the local electrochemistry under the disbonded coating to be suitable for SCC. The X70 pipeline steel would trangranularly crack in these conditions.