The influence of [(2-pyridin-4-ylethyl)thio] acetic acid (PI) and pyridine (P2) on the corrosion inhibition of steel in sulphuric acid solution is studied using weight loss, potentiodynamic polarisation and linear polarisation resistance (R-p) and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that PI is the best inhibitor and its inhibition efficiency (E%) increases with the increase of concentration. The highest E% of 82% is observed at 5 x 10(-3) M. Potentiodynamic polarisation studies clearly reveal that PI acts as a mixed inhibitor. The inhibitor studied reduces the corrosion rates. E% values obtained from various methods used are in good agreement. Adsorption of P1 on steel surface obeys to Langmuir adsorption isotherm. Effect of temperature indicates that E% decreases with temperature between 298 and 353 K. (c) 2004 Elsevier B.V. All rights reserved.