Corrosion resistance of stainless steel pipes in soil

Abstract

To be able to give safe recommendations concerning the choice of suitable stainless steel grades for pipelines to be buried in various soil environments, a large research programme, including field exposures of test specimens buried in soil in Sweden and in France, has been performed. Resistance against external corrosion of austenitic, super austenitic, lean duplex, duplex and super duplex steel grades in soil has been investigated by laboratory tests and field exposures. The grades included have been screened according to their critical pitting‐corrosion temperature and according to their time‐to‐re‐passivation after the passive layer has been destroyed locally by scratching. The field exposures programme, being the core of the investigation, uses large specimens: 2 m pipes and plates, of different grades. The exposure has been performed to reveal effects of aeration cells, deposits or confined areas, welds and burial depth. Additionally, investigations of the tendency of stainless steel to corrode under the influence of alternating current (AC) have been performed, both in the laboratory and in the field. Recommendations for use of stainless steels under different soil conditions are given based on experimental results and on operating experiences of existing stainless steel pipelines in soil.

Failure analysis of an oil pipe wall perforated by pitting corrosion

“…Comparatively speaking, the pitting corrosion on stainless steels has been studied extensively. Over the course of decades of research work into the pitting corrosion on stainless steels has revealed a considerable amount of information about pitting initiation process, pitting mechanism as well as pitting morphology . In regard to mild steel pipelines, there are still something unknown for researchers.…”

“…Among all types of corrosion attack, pitting corrosion is the cause of most failures . Additionally, pitting corrosion has also been found in some in‐service pipelines and failure of pipelines caused by localized corrosion typically has resulted in dramatic economic loss and serious social impact . Numerous parameters influence pitting corrosion rate such as temperature, pH, especially in the concentration of corrosive ions, and chloride ions are usually, although not always, the cause .…”

Soil impacts on UK infrastructure: current and future climate

“…Soil disturbance allows oxygen, through formed pore spaces, to reach exposed metal surfaces, as well as introducing foreign materials and organisms, both altering the soil chemistry (i.e. pH) (Bradford, 2001 Angular soil particles can score or pierce the passive protective layer of metallic pipes, having a profound effect on corrosion rates and leaving pipes exposed to potentially aggressive soils (Sjogren et al, 2011). Corrosion-resistant PVC pipes are also subject to the abrasive action of angular particles, leading to…”

Determination of adhesion between corrosion product film and carbon steel by a scratch test

“…As a quantitative measurement of coating/substrate adhesion, the scratch test has been extensively used 4–12, and established different calculation models of coating/substrate adhesion. Benjamin and Weaver 13 reported that full plastic deformation occurred before the thin film was peeled from the substrate.…”