In this work, the inhibition effect of borax and ethylene glycol (EG) on the corrosion behavior of carbon steel A106 was investigated in the solution containing 900 ppm sodium silicate and 100 ppm sodium chloride at 25 °C. For this purpose, the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were applied. The increase of EG concentration up to 50% by volume results the decrease of passive current density (ip) from 19.6 to 12.1 µA.cm-2 whilst its effect on the breakdown potential (Eb) was negligible. When borax concentration increases up to 450 ppm, the ip decreases significantly from 19.6 to 4.6 µA.cm-2, further addition of borax causes to markedly decrease of resistance against both uniform and pitting corrosion. Moreover, borax showed the best synergistic effect at 450 ppm concentration in 30% EG solution containing 900 ppm sodium silicate and 100 ppm sodium.

Keywords: Carbon steel, Sodium silicate, Ethylene glycol, Borax, Polarization, EIS

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