Amino acids modified konjac glucomannan as green corrosion inhibitors for mild steel in HCl solution

Kegui Zhang; Wenzhong Yang; Xiaoshuang Yin; Yun Chen; Ying Liu; Jinxun Le; Bin Xu

doi:10.1016/j.carbpol.2017.10.069

Amino acids modified konjac glucomannan as green corrosion inhibitors for mild steel in HCl solution

Carbohydr Polym. 2018 Feb 1:181:191-199. doi: 10.1016/j.carbpol.2017.10.069. Epub 2017 Oct 23.

Authors

Kegui Zhang¹, Wenzhong Yang², Xiaoshuang Yin¹, Yun Chen¹, Ying Liu¹, Jinxun Le¹, Bin Xu³

Affiliations

¹ College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 210009, China.
² College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 210009, China. Electronic address: yangwz@njtech.edu.cn.
³ Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing 210042, China.

PMID: 29253963
DOI: 10.1016/j.carbpol.2017.10.069

Abstract

Konjac glucomannan (KGM) was modified with amino acids to synthesize polysaccharide esters (KGMA and KGMH) which were evaluated as corrosion inhibitor for mild steel in 0.5M HCl solution by weight loss tests, Tafel curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The synthetic polymers were found to have the lower water absorbency and the higher water solubility than KGM. Gravimetric measurements showed the maximum efficiencies of KGMA and KGMH for decreasing the corrosion rate of metal at 2000ppm are up to 89.9% and 92.4%, respectively. Polarization curves indicated polysaccharide esters could retard both hydrogen evolution reaction and metal dissolution reaction and that the inhibitory effect was concentration dependent. Besides, EIS studies demonstrated the corrosion resistance of mild steel in hydrochloric acid was enhanced by polymer additives. The observations on mild steel surface by SEM suggested the metallic substrate obtained good protection against corrosion in inhibitor-containing HCl solution. The adsorptive behavior of polymer molecules including physisorption and chemisorption obeyed Langmuir isotherm and UV-vis spectra revealed the formation of inhibitor-ion complex. The better performance of KGMH on corrosion inhibition was attributed to the easier transfer of π-electron or n-electron, which was confirmed by quantum chemical calculations.

Keywords: Adsorption; Corrosion inhibition; Electrochemical technique; Konjac glucomannan; Mild steel.