Understanding of the Sour Resistance Improvement of an Industrial X52MS Line Pipe via Ni Addition

Abstract In this study it is shown that a light nickel addition improves the sour resistance of line pipe material via four point bending under severe sour environment. Only few references in the open literature treat the origins of this improved sour resistance. Here, the impact of nickel is investigated for an industrial X52MS line pipe steel in terms of hydrogen ingress and surface modification. The former is studied via permeation and interrupted testing with direct hydrogen measurements while the later is studied via Electron Probe MicroAnalyzer (EPMA), Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). It is shown that with Ni, the hydrogen uptake is reduced as well as the hydrogen coefficient of diffusion. The addition of Ni leads to a thinner and more compact corrosion layer as function of time when exposed to severe sour environment. Permeation results under sour and non-sour charging media are also discussed.