11074 Study on Factors Affecting Low CR Alloy Steels in a CO2 Corrosion System

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Product Number: 51300-11074-SG

ISBN: 11074 2011 CP

Author: Lining Xu, Taihui Chen, Wei Chang, Minxu Lu and Lei Zhang

Publication Date: 2011

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With better anti-CO₂ corrosion performance than carbon steel, low Cr (1%~5%) alloy steel has potential for use as pipeline steel to transport oil and gas. To understand the anti-corrosion mechanism of steels containing Cr, the formation of protective corrosion products was thoroughly studied. A large number of autoclave experiments simulating the oilfield environment had been carried out in the temperature range of 40-140° C. Further more, other factors affecting film formation, such as Cl- concentration (ranging from 10g/L to 50g/L), microstructure and Chromium content were studied.

The surface morphology and the composition of the corrosion product were analyzed using surface analytical techniques (SEM and EDS) and X-Ray diffraction (XRD), respectively. The result showed that, above 3%Cr addition to steels could remarkably improve the resistance to CO₂ corrosion due to three-dimensional mixed resistant networks within the corrosion products. With the increase of either temperature or Cl- concentration, maxium corrosion rates of 3Cr steel was observed. Otherwise, with the same chemical composition, the microstructure difference between 3Cr steels resulted in the different anti-CO₂ corrosion performance.

Keywords: CO₂ corrosion, low Cr alloy steels, resistance mechanism, factors