Eco friendly Chitosan Schiff bases for Enhanced Corrosion Resistance of Mild Steel in Acid Medium and Calcium Carbonate Scale Inhibition

Abstract

Chitosan, a versatile biopolymer was modified into its Schiff base derivatives using four newlinedifferent aldehydes viz., salicylaldehyde, Vanillin, thiophene- 2- carboxaldehyde, pyrrole 2- newlinecarboxaldehyde. Chitosan Schiff bases (ChSSB, ChVSB, ChTSB, ChPSB) were synthesized by newlinecondensing theactive carbonyl group of aldehydes with free amino groups of Chitosan. The newlinesynthesized Chitosan Schiff bases were characterized using Elemental, spectral (UV, FTIR) and SEM newlineanalysis to confirm the incorporation of aldehydes onto the Chitosan backbone through imine newlinelinkages. The thermal stability of the Chitosan Schiff bases was analyzed by thermogravimetric newlineanalysis. The corrosion inhibition performance of Chitosan Schiff bases was explored for mild steel in newline1M HCl solution using weight loss, electrochemical impedance spectroscopy and potentiodynamic newlinepolarization methods at room temperature and at higher temperature range of 313-343K with different newlineconcentrations (100-1500ppm). Inhibition efficiency of the inhibitors increased with increase in newlineconcentration of all the studied concentration within the range of 100-1500ppm. All the Schiff base newlineinhibitors showed better inhibition performance of around 90% at the concentration of 1500ppm. newlinePotentiodynamic polarization analysis revealed that Chitosan Schiff bases behaved as a newlinemixed type inhibitor. The protective film formed on the metal was stable till 323K and then tend to newlinedesorb at higher temperatures. Electrochemical impedance spectroscopy analysis (EIS) revealed an newlineincrease in polarization resistance due to the adsorbed inhibitor molecules. The temperature effect on newlinethe inhibition process was also tested by constructing Arrhenius plot and Transition plot. The data newlineobtained from the temperature studies of weight loss technique were fitted to various isotherms and newlinethe best fit was found to be Temkin isotherm for all the studied Chitosan Schiff bases. newlineThermodynamic parameters of adsorption were calculated which indicated the chemisorptive nature newlineof adsorption of the Schiff base polymers.