DefinePK

Abstract

The mechanism and efficiency of inhibition of the ethanol extract from galangal rhizome on the carbon steel API 5L X65 corrosion in an environment appropriateness to the conditions of a petroleum well had been studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (Tafel plot). The results showed that the ethanol extract from galangal rhizome is good inhibitor. The inhibition efficiency increased as the galangal extract concentration was increased and the inhibition reached its optimum at 200 ppm by 87%. Potentiodynamic polarization studies clearly reveal that galangal rhizome acts essentially as cathodic-type inhibitor. The experimental impedance data were analyzed according to a proposed equivalent circuit model for the electrode/electrolyte interface, its show that the corrosion inhibition mechanism took place through the adsorption process which formed an uneven protective film on the carbon steel surface. The adsorption took place physically following Langmuir's adsorption isotherm with the adsorption energy of -14.96 kJ.mol-1.