Abstract
Background: Organic inhibitors used to reduce the degradation rate of steel structures in acid solution are highly toxic to human and environment. Natural products such as plants or seeds extracts are being investigated as green inhibitor to combat this global environmental threat. A homeopathic medicine, commonly used in preventing gas and acidity problems of human beings is investigated to reduce similar gas and acidity problems of acid steel tank.
Methods: The study was conducted, with low carbon steel, in 0.5 to 2 N HCl with variation of drops of homeopathic medicine with constituents: Lycopodium, Robinia, Natrumphos and carboveg. The corrosion rates of test specimens were determined by performing electrochemical polarization tests with computer controlled Gamry machine, with variation of concentration of acids as well as inhibitor. The study of adsorption of inhibitor on metal surface was also conducted and the adsorption isotherm fitting the data was evaluated to under the science of corrosion inhibition.
Results: The results shows that increase in inhibitor concentration decreases the rate of degradation. But there is an optimum concentration at which the inhibitor effect is maximum, beyond that the corrosion rate again increases. The adsorption study shows that the mechanism of corrosion inhibitor is due to physical adsorption, following Langmuir and Temkin adsorption isotherms. The metallic surface in acid before and after addition of inhibitor, under optical microscopy, clearly reveals that the corrosion process has been retarded by the adsorption of the inhibitor.
Conclusion: A new green inhibitor has come up in a homeopathic medicine in inhibiting the acid corrosion of carbon steel. The percentage of corrosion retardation depends on the concentration of acid as well as the amount of inhibitor added.
Keywords: Acid corrosion, adsorption isotherm, green inhibitor, homoeopathy medicine.
Graphical Abstract
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