CORROSION INHIBITION EFFECT OF THIOUREA ON MILD STEEL IN HYDROCHLORIC ACID CONTAMINATED WITH CHLORINE

Inexpensive industrial hydrochloric acid, containing chlorine (Cl2) and other chlorinated organic compound contaminants, generally comes from the recovery of chlorinated organic compounds. The objective of this work is to evaluate, based on laboratory tests, the performance of the corrosion inhibitor (thiourea) in protecting carbon steel when immersed in hydrochloric acid contaminated with chlorine. In this evaluation, mass loss tests and electrochemical polarization tests were conducted under the following conditions: a concentration of hydrochloric acid of 5, 10, and 15% (by mass); chlorine (Cl2) was added to the acid in quantities of 50 - 5000 mg/L; the concentrations of thiourea were 250, 500, and 1000 mg/L; and the temperature was maintained at 25°C. Gravimetric and polarization tests carried out using mild steel coupons show a significant loss of thiourea inhibitory protection because there is an increase in the concentration of hydrochloric acid associated with an increase in chlorine content.