4.2. Potentiodynamic Polarization Measurement

The metal corrosion inhibition ability of inhibitors was studied by the polarization curve method on the PGS-HH3 device of the Vietnam Academy of Science and Technology at temperatures ranging from 30 to 60 °C with a step size of 10 °C. Electrochemical measurements were performed on the CPAiocHH5B-meter with a three-electrode system, in which the working electrode was low carbon steel, the comparison electrode was Ag/AgCl in saturated KCl, and the counter electrode was stainless steel with a large area.

Corrosion potential was scanned from −1.00 to 0.20 V with a sensitivity of 7. Investigated concentrations of inhibitors were 1.0 × 10^–5, 5.0 × 10^–5, 1.0 × 10^–4, and 2.0 × 10^–4 M. Ethanol was added into the solution to ensure the solubility of inhibitors. The surface of the working electrode was abraded with metallographic emery paper and then was washed with distilled water, acetone, and finally was dried.

The corrosion inhibition efficiency (H %) was calculated by the following formula⁴⁴

where i_corr is the corrosion current density in the absence of inhibitors (mA cm^–2) and i_inh is the corrosion current density in the presence of inhibitors (mA cm^–2).

Surface coverage was calculated based on the following equation¹⁶