Abstract

Results of two studies conducted as part of the Strategic Petroleum Reserve (SPR) Pipeline Corrosion Control Program are reported. These studies focused on evaluation of rotary-applied concrete materials for internal pipeline protection against the erosive and corrosive effects of flowing brine. The study also included evaluation of liners applied by hand on pipe pieces that cannot be lined by rotary methods. Such pipe pieces include tees, elbows and flanged pipe sections. Results are reported from a corrosion survey of 17 different liner formulations tested at the-Big-Rill SPR Site. Testing consisted of electrochemical corrosion rate measurements made on lined pipe sections exposed, in a test manifold, to flowing SPR generated fluids. Testing also involved cumulative immersion exposure where samples were exposed to static site-generated brine for increasing periods of time. Samples were returned to the laboratory for various diagnostic analyses. Results of this study showed that standard calcium silicate concrete (API RP10E) and a rotary calcium aluminate concrete formulation were excellent performers. Hand-lined pipe pieces did not provide as much corrosion protection. The focus of the second part of the study was on further evaluation of the calcium silicate, calcium aluminate and hand-applied liners in actual SPR equipment and service. It was a further objective to assess the practicality of electrochemical impedance spectroscopy (EIS) for field corrosion monitoring of concrete lined pipe compared to the more well-known linear polarization technique. This study showed that concrete linings reduced the corrosion rate for bare steel from 10 to 15 mils per year to 1 mil per year or less. Again, the hand-applied liners did not provide as much corrosion protection as the rotary-applied liners. The EIS technique was found to be robust for field corrosion measurements. Mechanistic and kinetic corrosion rate data were reliably obtained. Document type: Report

Abstract

Centrifugally-cast concrete liners applied to the interiors of plain steel pipe sections were tested for corrosion performance in brine solutions. An American Petroleum Institute (API) standard concrete, with and without additions of a styrene-butadiene copolymer latex, was subjected to simulated service and laboratory tests. Simulated service tests used a mechanically pumped test manifold containing sections of concrete-lined pipe. Linear polarization probes embedded at steel-concrete interfaces tracked corrosion rates of these samples as a function of exposure time. Laboratory tests used electrochemical impedance spectroscopy to study corrosion occurring at the steel-concrete interfaces. Electron probe microanalysis (EPMA) determined ingress and distribution of damaging species, such as Cl, in concrete liners periodically returned from the field. Observations of concrete-liner fabrication indicate that latex loading levels were difficult to control in the centrifugal-casting process. Overall, test results indicate that latex additions do not impart significant improvements to the performance of centrifugally cast liners and may even be detrimental. Corrosion at steel-concrete interfaces appears to be localized and the area fraction of corroding interfaces can be greater in latex-modified concretes than in API baseline material. EPMA shows higher interfacial Cl concentration in the latex-modified concretes than in the API standard due to rapid brine transportmore » through cracks to the steel surface.« le Document type: Report