51313-02698-SSC Resistance of 316Ti in Brine under Highly Sour Conditions

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Product Number: 51313-02698-SG

ISBN: 02698 2013 CP

Author: Gerit Siegmund

Publication Date: 2013

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The applicability of the alloy UNS S 31635 (316Ti 1.4571) in chloride containing sour environments is presently controversially discussed. According to ISO 15156 Part 3 this material shall be used in chloride-containing media only under H2S partial pressures up to 1 bar. However this material has been used for decades in many highly sour industrial environments without any reported failure. The ongoing discussions on the application limits of the alloy UNS S 31635 prompted new experimental work to evaluate the SSC and pitting susceptibility of this material in highly sour brines at room temperature. Round tensile specimens were subjected in triplicate for each set of conditions under 70% and 90% of the actual yield stress for 720 h fully submerged in brine with 1.000 mg/L and 30.000 mg/L chloride respectively in equilibrium with a gas phase containing 16 bar H2S + 16 bar CO2 and 16 bar H2S + 8 bar CO2 respectively. None of the tensile bars showed any indication of SCC or pitting and the integral corrosion rates ranged between 0.4 and 4 µm/y depending on the system’s corrosion severity. This is in agreement with the many years of service experience. The results indicate that the tested type of material can be used in sour environments up to 16 bar H2S in the presence of chloride concentrations up to 30.000 mg/L.