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Received: September 07, 2018; Revised: October 05, 2018; Accepted: October 08, 2018
Abstract: Metallic structures in the oil and gas production undergo severe degradation due to sweet and sour corrosion caused by the presence of CO2 and H2S in the fluid environment. The corrosion behavior of 304 austenitic stainless was investigated in the presence of varying concentrations of CO2 or H2S and CO2 + H2S to understand the effect of the parameters either individually or in combination. Potentiodynamic polarization study revealed that a small amount of CO2 aided in the formation of calcareous deposit of protective layer on passive film of 304 steel, while increase in CO2 concentration ruptured the layer resulting in sweet corrosion. The presence of S2- damaged the passive and protective layer of the steel and higher levels increased the degradation rate. Electrochemical impedance studies revealed lower polarization resistance and impedance at higher concentration of CO2 or H2S, supporting the outcomes of polarization study. XRD analysis revealed different types of iron carbides and iron sulphides corresponding to sweet and sour corrosion as the corrosion products,respectively. SEM analysis revealed the presence of uniform, localized and sulphide cracking in sour corrosion and general corrosion with protective carbide layer amid for sweet corrosion.