INHIBITION EFFICIENCY IN PETROLEUM ENVIRONMENT BY DIPHENYLAMINE
RANA AFIF ANAEE *
Department of Materials Engineering, University of Technology, Iraq
MOHAMMED H. HAFIZ
College of Engineering, Iraqi University, Iraq
RANA S. NOOR
Al-Faris Company, Ministry of Industry and Minerals, Iraq
*Author to whom correspondence should be addressed.
Abstract
The inhibition properties of steel (A515) in sour medium by diphenylamine (DPA) were studied with four concentrations namely 1x10-5, 1x10-4, 1x10-3 and 1x10-2 M at (75ºC) using Potentiostat/Galvanostat instrument. FTIR spectra were used to identify the inhibited surfaces. These methods were employed reasonably agree and indicate that DPA act as good inhibitor with protection efficiencies ranged between 65.24 to 85.81% for experimental concentrations. Thermodynamics of adsorption revealed that the change in free energy was negative indicating spontaneous process of adsorption. Negative values of the change in enthalpy and entropy confirm the exothermic process and decreasing in disorder of inhibition with DPA.
Diphenylamine is obeys Langmuir adsorption isotherm and acts as mixed type inhibitor, which affects both Tafel slopes. Protection efficiency calculations indicate that 1x10-2 M gave best efficiency equal to 85.81%.
Keywords: Corrosion inhibition, sour medium, amines, Langmuir isotherm