The inhibition effect of propargyltriphenylphosphonium bromide (PgTPhPBr), with a structure (CHdropC-CH2-)(C6H5-)(3) P+Br, on the electrochemical and corrosion behavior of three 0.1, 0.5 and 1.0% C-steels and pure iron in deaerated 1 M H2SO4 solution at different temperatures was studied using linear polarization resistance, polarization curves and SEM investigations. It was found that 0.5% C-steel (CS2) has high density of active sites on the surface leading to high corrosion rate. PgTPhPBr acted as a mixed type inhibitor with anodic predominance in case of pure iron and a mixed type inhibitor in case of C-steels. The inhibition efficiency of PgTPhPBr increased with increasing temperature up to 60degreesC. Adsorption of the inhibitor was found to follow the Langmuir's isotherm. This inhibitor was more efficient for CS2 than for other samples at different temperatures. It was proposed that PgTPhPBr decreases the corrosion rate through the reduction mechanism of metal reactivity. (C) 2002 Elsevier Science B.V. All rights reserved.