This paper summarizes the experimental and theoretical evidence showing that, in permanent immersion, the protectiveness of corrosion layers can only be due to diffusional transport phenomena in the liquid phase. This gives rise to the new concept of a “liquid surface state”. A consequence is that any imposed polarization can prove to be instantaneously destructive. It is therefore not possible to plot standard polarization curves, and they must be replaced by “pseudo-polarization” curves representing the trajectory of the free corrosion point in the Tafel reference coordinates.

Protectiveness of Corrosion Layers

Grooving corrosion of electric-resistance-welded oil well casing of J55 steel

Grooving corrosion of oil coiled tubes manufactured by electrical resistance welding

While pipelines offer a safe, cost-effective way to move natural gas and hazardous liquids, pipeline leaks and ruptures can result in disastrous consequences. Pipelines can be susceptible to different metallurgical failure mechanisms including but not limited to manufacturing defects, third party damage, and corrosion. This chapter outlines common pipeline failure mechanisms and provides selected case studies, which highlight typical issues that can result in pipeline leaks and ruptures. Understanding these failure mechanisms is critical to mitigating risk of future incidents and managing the future integrity of the pipeline.

Failure analysis of oil and gas transmission pipelines

Identification of the selective corrosion existing at the seam weld of electric resistance-welded pipes

When exposed to neutral, salt-containing waters, electric resistant welded pipe in carbon and low alloy steels with increased sulfur contents may suffer preferential corrosion attack in the weld area. Because of its appearance, this type of corrosion is called grooving corrosion. The susceptibility to grooving corrosion may be determined and quantitatively described by means of an accelerated potentiostatic exposure test. The importance of type, concentration, and temperature of the electrolytic solution; potential; test duration; and the sulfur content of the steel in the accelerated corrosion test and the susceptibility of steels to grooving corrosion are described. Line pipe in high frequency inductive (HFI) welded carbon and low alloy steels are resistant to grooving corrosion particularly because of their low sulfur content.

G Herbsleb

Papers

The resistance of high frequency inductive welded pipe to grooving corrosion in salt water