Anti-corrosion performance of the synergistic properties of benzenecarbonitrile and 5-bromovanillin on 1018 carbon steel in HCl environment.

The synergistic properties of the combined admixture of benzenecarbonitrile and 5-bromovanillin (BNV) on the corrosion resistance of 1018 carbon steel in 1 M HCl was analysed with potentiodynamic polarization technique, weight loss method, micro-analytical studies and ATF-FTIR spectroscopy. Results obtained show the admixed organic compound was effective with optimal corrosion inhibition values of 99.33% and 90.34% at 1.25% BNV concentration from both electrochemical methods due to the effective inhibition action and passivation characteristics of the protonated inhibitor molecules in the acid solution. Primary amines, stretch alkyl halides and C-H triple bond functional groups of the molecules were observed to actively adsorb during the corrosion inhibition reaction from ATF-FTIR spectroscopic analysis. Calculations from thermodynamic evaluation confirmed cationic adsorption mechanism to be chemisorption obeying the Langmuir and Frumkin adsorption isotherm. Micro-analytical observations of the inhibited carbon steel morphology significantly contrast the unprotected steel due to visible surface deterioration and presence of micro/macro-pits. The organic derivatives showed mixed type inhibition reactions.