Abstract

Effect of Cl- concentration on pitting susceptibility of UNS S31603 stainless steel was evaluated by immersion testing. Initiation and growth of pitting on austenitic stainless steel exposed to a sour environment was studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and electrochemical measurement. The results show that the pitting potential of UNS S31603 steel decreases with a rise of Cl- concentration, and the pitting susceptibility increases significantly. In pit initiation, there exist competitive adsorption between Cl- and H2S. When Cl- concentration reaches a certain level, Cl- occupies most of the adsorption sites on the surface of passive film. This can impede the reaction between H2S and the passive film, however, the corrosion process is inhibited. With the further increases of the Cl- concentration, due to the formation of soluble complexes via the reaction between Cl- and the metal, the dissolution of passive film increases and the corrosion process is accelerated. The pitting depth of UNS S31603 stainless steel increases with the increasing Cl- concentration under a sour environment, and the pitting grows inward.

Keywords:
riser corrosion, pipeline corrosion, texas 77084, initiation, publication division, vacancy, manuscript, capacitance, cavity, passive film
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Materials and corrosion, Corrosion inhibition and management (including H2S and CO2)
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2015. NACE International
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