Mitigation of magnesium corrosion in the presence and absence of KI using an ionic liquid in NaCl solutions

Abstract

Hydrogen evolved from corroding magnesium surfaces was collected and used to evaluate the effect of ethyl dimethyl propylammonium bis (trifluoromethyl sulfonyl) imide (EDMPA-TFSI) on magnesium corrosion in 1.0 M NaCl solution in the presence and absence of potassium iodide (KI) at temperatures of 303 K and 333 K. The results showed that EDMPA-TFSI retarded magnesium corrosion rates, recording maximum inhibition efficiencies of 85.2 % and 86.6 % at 303 K and 333 K, respectively, in the absence of KI. However, in the presence of KI, the inhibition efficiency increased to 91.7 % at 303 K but decreased to 29.8 % at 333 K, respectively. This indicates an antagonistic effect of KI on the inhibition efficiency of EDMPA-TFSI at elevated temperatures and a synergistic effect of KI at ambient temperature. The corrosion kinetics in the presence of EDMPA-TFSI were consistent with first-order reaction kinetics. Thermodynamic parameters such as Activation energy (ranged from 40.77 to 134.33 kJ/mol) and Heat of adsorption Q_ads (ranged from 6.05 to -67.19 kJ/mol) indicate that EDMPA-TFSI transitions from a mixed physisorption and chemisorption mechanism at lower concentration to predominant chemisorption at higher concentrations of EDMPA-TFSI. Results indicate that EDMPA-TFSI can be used as corrosion inhibitors for magnesium in aqueous salt environments.