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51318-10548-Localized Corrosion of Mild Steel in Marginally Sour Environments

In the current study, mild steel specimens (API 5L X65) were exposed to a 1 wt% NaCl solution sparged at 0.096 MPa pCO2 and 15 ×10-6 MPa or less pH2S (≤ 150 ppm H2S/CO2).

Product Number: 51318-10548-SG
Author: Saba Navabzadeh Esmaeely / Wei Zhang / Bruce Brown / Marc Singer / Srdjan Nesic
Publication Date: 2018
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Localized corrosion has been a challenge for the integrity of mild steel pipelines, specifically at operating conditions where a trace amount of H2S is present alongside CO2 at lower temperatures. The presence of H2S leads to formation of a protective iron sulfide layer that decreases the general corrosion rate; however, a trace amount of H2S may only lead to a partially protective mackinawite layer that could result in localized corrosion. In the current study, mild steel specimens (API 5L X65) were exposed to a 1 wt% NaCl solution sparged at 0.096 MPa pCO2 and 15 ×10-6 MPa or less pH2S (≤ 150 ppm H2S/CO2). At pH 5.0 and 30oC the bulk solution was under-saturated with respect to iron sulfide - mackinawite and iron carbonate. At these marginally sour conditions, a H2S/CO2 threshold of approximately 100 ppm was deduced, below which localized corrosion happened. At the tested conditions no localized corrosion occurred for the same environmental conditions when H2S/CO2 ratio was above 100 ppm or when there was no H2S present.

Localized corrosion has been a challenge for the integrity of mild steel pipelines, specifically at operating conditions where a trace amount of H2S is present alongside CO2 at lower temperatures. The presence of H2S leads to formation of a protective iron sulfide layer that decreases the general corrosion rate; however, a trace amount of H2S may only lead to a partially protective mackinawite layer that could result in localized corrosion. In the current study, mild steel specimens (API 5L X65) were exposed to a 1 wt% NaCl solution sparged at 0.096 MPa pCO2 and 15 ×10-6 MPa or less pH2S (≤ 150 ppm H2S/CO2). At pH 5.0 and 30oC the bulk solution was under-saturated with respect to iron sulfide - mackinawite and iron carbonate. At these marginally sour conditions, a H2S/CO2 threshold of approximately 100 ppm was deduced, below which localized corrosion happened. At the tested conditions no localized corrosion occurred for the same environmental conditions when H2S/CO2 ratio was above 100 ppm or when there was no H2S present.

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51318-10568-Quality & Performance Review of Duplex Stainless Steel Products – An End Users Perspective

Product Number: 51318-10568-SG
Author: Janardhan Rao Saithala / Gurram Bhaskar Rao / Manoj Suryanarayana / Talal Nebhani / Pedro Rincon / Nasser Behlani / Mohammed Ghafri / Amjad Kharusi
Publication Date: 2018
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