Investigation of some oleochemicals as green inhibitors on mild steel corrosion in sulfuric acid |
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Authors: | M Z A Rafiquee Sadaf Khan Nidhi Saxena and M A Quraishi |
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Affiliation: | (1) Corrosion Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, 20 2002, India;(2) Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi, 221 005, India |
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Abstract: | The inhibitive effect of four oleo chemicals (namely; 2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl-1,3-imidazoline (UDI),
2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI)), regarded as green inhibitors, were studied for the corrosion
protection of mild steel in 0.5 M H2SO4. The methods employed were weight loss, potentiodynamic polarization and electrochemical impedance techniques. Scanning electron
microscopy (SEM) was carried out on the inhibited and uninhibited metal samples to characterize the surface. The purity of
synthesized inhibitors was checked by FT-IR and NMR studies. The inhibition efficiency increased with increase in inhibitor
concentration, immersion time and decreased with increase in solution temperature. No significant change in IE values was
observed with increase in acid concentration. The best performance was obtained for UDI possessing 96.2% inhibition efficiency
at 500 ppm concentration. The adsorption of the compounds on the mild steel surface in the presence of sulfuric acid obeyed
Langmuir’s adsorption isotherm. The values obtained for free energy of adsorption and heats of adsorption suggest physical
adsorption. The addition of inhibitor decreased the entropy of activation suggesting that the inhibitors are more orderly
arranged along the mild steel surface. The potentiodynamic polarization data indicate mixed control. The electrochemical impedance
study further confirms the formation of a protective layer on the mild steel surface through the inhibitor adsorption. |
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Keywords: | Corrosion and oxidation Metals and alloys Kinetics Surfaces Thin films Green inhibitors |
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