Tecnologia em Metalurgia, Materiais e Mineração (Sep 2012)

EVALUATION OF CORROSION IN WELD REGION AND BASE METAL OF API 5L X80 PIPE IN MEDIUM CONTAINING HYDROGEN SULPHIDE

  • Bruno Nagle Armendro,
  • Mario Fernando González Ramírez,
  • Hélio Goldenstein,
  • Neusa Alonso-Falleiros

DOI
https://doi.org/10.4322/tmm.2012.031
Journal volume & issue
Vol. 9, no. 3
pp. 220 – 228

Abstract

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The objective of this study is to compare the corrosion resistance of the base metal (MB) and weld region (RCS) of a X80 pipeline in three types of aqueous solution of acetic acid (CH3COOH) 0,5% by weight: naturally aerated, non-aerated and non-aerated with H2S. Linear polarization is employed for it determinates Polarization Resistance (Rp) which allows comparing the corrosion resistance of steel in different conditions. The results show that Rp practically does not change with the immersion time (until 8 hours), for both regions. The two regions have higher Rp in non-aerated aqueous solution, intermediate Rp in non-aerated with H2S and lower Rp in naturally aerated; this is due the effect of oxygen in cathodic reactions and shows that H2S can accelerate slightly the corrosion. The RCS has greater Rp than the MB for any aeration conditions. The presence of alloying elements in RCS justifies this behavior. The morphology of corrosion was examined under an optical microscope (MO) and shows that uniform corrosion is predominant.

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