Corrosion protection of copper by self assembled monolayers

Abstract

Self assembled monolayer (SAM) of 3-methyl-5-octadecylsulfanyl-[1,2,4]triazole-4-ylamine (MOSTY) was formed on the copper surface and the optimum conditions of formation of SAM were established. Corrosion behaviour of copper with the SAM was investigated in 0.02 M aq. HCl (acidic) and 0.02 M aq. NaCl (neutral) solutions. Weight-loss measurements, potentiodynamic polarization studies and electrochemical impedance studies were carried out in order to investigate the effect of MOSTY SAM on the corrosion protection of copper. Appropriate equivalent circuit models were used for impedance measurements of bare copper and the SAM covered copper in the chosen aggressive environments. These studies revealed the corrosion inhibition efficiency of SAM to an extent of 98% in 0.02 M aq. NaCl and 86% in 0.02 M aq. HCl environments. Potentiodynamic polarization studies revealed that this SAM controls both the anodic and cathodic reactions and thus protects copper from corrosion. The X-ray photoelectron spectroscopy (XPS) was used to characterize the SAM. The XPS revealed the presence of various elements viz. carbon, nitrogen and sulphur in the SAM. Shifts in binding energies of nitrogen and sulphur were interpreted. The inhibition of copper dissolution was interpreted due to the chelating effect of Cu (I) ions with the chemisorbed ligand molecules forming a complex of SAM on copper surface.