Thermodynamic characterisation of steel corrosion and inhibitor adsorption of pyridazine compounds in 0.5 M H2SO4

The influence of 5-(2-chlorobenzyl)-6-methylpyridazine-3(2H)-thione (P1) and 5-(4-chlorobenzyl)-6-methylpyridazine-3(2H)-thione (P2) on the corrosion of steel in 0.5M H2SO4 solution has been studied using weight loss measurements at various temperature. The inhibiting action is more pronounced with P1 than P2. The inhibition efficiency increases with P1 concentration to attain the maximum value of 100% at 5 × 10− 4 M. P1 adsorbs on the surface of steel according to the Langmuir isotherm model. The thermodynamic data of activation and adsorption are determined.