Adsorption and Thermodynamic Characteristics of Plumeria rubra Plant Extracts on Mild Steel Corrosion in Industrial Water Medium

The inhibition effect of Plumeria rubra (PR) extracts on the corrosion of mild steel in industrial water medium was studied by mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that the protection efficiency increased with increase in inhibitor concentration and decreased with temperature. Electrochemical impedance spectroscopic measurements indicated that charge transfer resistance increases with increasing inhibitor concentration. The adsorption of PR extracts on mild steel surface obeys Langmuir isotherm model. Potentiodynamic polarization studies revealed that PR extracts act as a mixed-type inhibitor. Scanning electron microscopy (SEM) was used to analyze the surface adsorbed film.