Effects of H2s and pH on Tafel Slopes in Electrochemical Corrosion of High Strength Carbon Steel S-135 in Alkaline Brines. (29th August 2016)

• Record Type: Journal Article
• Authors: Feng, Ruishu; Beck, Justin; Ziomek-Moroz, Margaret; Lvov, Serguei N.
• Is Part Of: ECS transactions. Volume 72:Number 17(2016)
• Page Start: 59
• Page End: 71
• Publication Date: 2016-08-29
• Subjects: Electrochemistry -- Periodicals; Electrochemistry; Periodicals; Electronic journals; Electronic journal; 541.37
• DOI: 10.1149/07217.0059ecst
• Languages: English
• ISSNs: 1938-5862

Abstract

Abstract : Effects of H2 S and pH on electrochemical corrosion of high-strength low-alloy carbon steel, Grade S-135, were investigated through Tafel slopes. Linear sweep voltammetry (LSV) was conducted in 5 %wt. NaCl solutions of pH 7.9, 10.7, and 12.4 with four H2 S partial pressures ( p H2S ) ranging from 0 to 69 kPa at 85 o C after 60 hours of exposure. Anodic limiting current was observed without H2 S, but disappeared at higher p H2S . Cathodic LSV plots did not show limiting currents, suggesting that H2 O was the main reactant for the hydrogen evolution reaction at high pH. Both anodic and cathodic currents increased at 69 kPa p H2S compared to 0 kPa. Electrochemical reaction mechanisms were discussed based on anodic and cathodic Tafel slopes. The Tafel slopes from LSV were generally larger than those obtained from electrochemical frequency modulation. Different Tafel slopes could result in a discrepancy in corrosion rate by a factor of 5.