The Effect of Organic Inhibitors on the Corrosion of Mild Steel in Varying Crude Oil–Brine Emulsions: The Electrochemical Protocol Selection

Corrosion inhibitors are widely used in oil production, transportation, and refining, where crude oil–brine emulsions complicate electrochemical testing because of their heterogeneity and low conductivity. This study examined the use of Tafel polarization and electrochemical impedance spectroscopy to assess mild steel corrosion in brine and crude oil–brine emulsions in the presence of Nalco EC 1010B and Scimol OR 2001. Emulsions with a continuous conductive phase were tested directly, whereas the brine phase of reverse emulsions was separated before measurement. In brine, both inhibitors provided more than 80% protection at a concentration of 20 mg/L. At this concentration, corrosion rates in the inhibited direct emulsion and the brine phase separated from the reverse emulsion were approximately 0.20–0.25 mm/year, comparable to those in inhibited brine under similar conditions. In stable emulsions, the surfactant also affected steel corrosion, complicating the assessment of inhibitor performance. These results indicate that measurements in brine can guide the selection of inhibitor concentrations for direct and reverse emulsions under the conditions investigated.