Pyrazole Derivatives as Corrosion Inhibitor for C- Steel in Hydrochloric Acid Medium

5-Chloro-1-Phenyl-3-methyle Pyrazolo-4-methinethiosemicarbazone was investigated as corrosion inhibitors for carbon steel in HCl by chemical and electrochemical method. It has been observed that corrosion rate decreases and inhibition efficiencies and surface coverage degree increases with increasing in inhibitor concentration and temperature. The apparent activation energy (Ea) and other thermodynamic parameters have also been calculated. The recorded electrochemical data indicated the basic modification of steel surface as a result in a decrease in the corrosion rate. The polarization data indicated that the used compound act as mixed type inhibitors. The slopes of the cathodic and anodic Tafel lines (Pc, Pa) are approximately constant and independent of the inhibitor concentrations. The inhibition occurs through adsorption of the inhibitor molecules on the metal surface without modifying the mechanism of corrosion process. SEM studies revels the formation of passive film on the metal surface.