The effect of 1-{[benzyl-(2-cyano-ethyl)-amino]-methyl}-5-methyl-1H-pyrazole-3-carboxylic acid methyl ester (P1) and 1-{[benzyl-(2-cyano-ethyl)-amino]-methyl}-5-methyl-1H-pyrazole-3-carboxylic acid ethyl ester (P2) was evaluated as corrosion inhibitors of steel in molar hydrochloric using weight loss measurements and electrochemical polarisation. The results obtained reveal that those compounds reduce the corrosion rate. The inhibiting action increases with the concentration of pyrazole compounds to attain 98.5 % at the 10-3 M of (P2). The increase in temperature leads to a decrease in the inhibition efficiency of the compounds in the temperature range 308 - 353 K. The adsorption isotherm of inhibitors on the steel has been determined. The thermodynamic data of activation and adsorption are determined.
