On the influence of crystallographic texture on pitting corrosion in pipeline steels

The influence of crystallographic texture on pitting corrosion is investigated in an API 5L X52 pipeline steel through crystallographic texture and electrochemical studies. Test samples of the studied steel were obtained with similar microstructure and different texture by means of different thermomechanical processes. The texture was characterized by means of X-ray pole figure measurements. The texture-dependent resistance of each sample to pitting corrosion was predicted using a function and an index which combine the susceptibility of crystallographic planes to anodic dissolution and their relative abundance at the material surface, this latter determined by the volume fraction of each texture fiber in the steel. The actual susceptibility of each sample to pitting corrosion was determined by means of cyclic potentiodynamic polarization measurements in two solutions emulating pipeline corrosion environments. The pitting susceptibility predicted from the texture measurements was in good agreement with the susceptibility determined from the cyclic polarization tests. Although the anisotropic nature of anodic dissolution of iron has been known for decades, the use of the crystallographic texture to predict the pitting resistance of pipeline steels conveys a statistical significance not reported until now.