Vitamin B9 as a new eco-friendly corrosion inhibitor for copper in 3.5% NaCl solution

Abstract

Folic acid salt (sodium folate) have been studied as an eco-friendly and non-toxic copper corrosion inhibitor in 3.5 % NaCl solution. Electrochemical impedance spectroscopy, polarization resistance, and weight-loss measurements show that the inhibitor efficiency increases with the concentration increase (the highest value- 96 % was reported for 16 mM sodium folate solution after 24 h). EIS data indicate that sodium folate is a barrier inhibitor. The standard Gibbs free energy of adsorption obtained using the Langmuir model (–27.5 kJ/mol) suggests that both chemisorption and physisorption may occur. The decrease in the inhibitor efficiency with temperature increase (the temperature coefficient of corrosion inhibition is –0.0045 1/oC) shows that the physical interactions between the inhibitor and metal surface dominate in the studied system. Potential chemical changes in the sodium folate solution were investigated using UV–VIS spectroscopy. Furthermore, the copper surface after immersion in the presence and absence of inhibitor was characterized with scanning electron microscopy, energy-dispersive X-Ray spectroscopy, and microscopic photographs. The protection of copper elements using sodium folate was found to be a promising method that is worth further development.