الفهرس 
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Abstract
Inhibition of the carbon steel corrosion in 0.5 M HCl by the some pharmaceutical compounds named Actonel, Fosamax &Etidron as indicated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation method (EFM) and surface examination using SEM & EDX techniques were found to depend on the number of adsorption sites in the molecule and their charge density, molecular size and stability of these additives in acidic solution. The results of weight loss showed that the inhibition efficiency increases with increasing the inhibitor concentration, while it decreases with increasing the temperature. Potentiodynamic polarization studies have shown that these compounds suppress both the cathodic and anodic processes and thus acted as mixed-type inhibitors. The adsorption of these compounds on carbon steel surface was found to follow the Langmuir isotherm. The effect of temperature on corrosion inhibition has been studied and thermodynamic activation and adsorption parameters were calculated and discussed. SEM analysis showed that the investigated pharmaceutical compounds were adsorbed on the metal surface forming a thin layer by which metal was protected from corrosion. The calculated inhibition efficiency obtained from weight loss, potentiodynamic polarization, EIS and EFM measurements are in good agreement. where the order of inhibition efficiency obtained from all measurements follow the order: