Abstract Benzotriazole and some of its derivatives cause inhibition of corrosion of reinforcing steel in saturated naturally aerated Ca(OH)2 solutions contaminated by Cl−. The inhibition efficiency of these compounds depends on both the inhibitor type and concentration, as well as, on the chloride ions content. Inhibition by these compounds is assumed to take place through the formation of iron-chloro-benzotriazoles complexes and/or the adsorption of the deprotonated species on the steel surface according to Langmuir’s isotherm. The thermodynamic parameters Kads and ΔG°ads for the adsorption process are calculated and discussed. Benzotriazoles shift the pitting corrosion potential into the noble direction accounting for increased resistance to pitting.