Effect of N-cetyl-N,N,N-trimethylammonium bromide and orthophenylenediamine on the corrosion inhibition of carbon steel in 1 mol/L HCl

Abstract

Inhibition studies of N-cetyl-N,N,N-trimethylammonium bromide (CTAB) and orthophenylenediamine (OPD) have shown that they were effective inhibitors of corrosion of carbon steel in HCl. The inhibitive behaviour of OPD with CTAB on the corrosion of carbon steel in 1 mol/L HCl was studied by gravimetric weight loss, potentiodynamic polarization, and electrochemical impedance measurements. Inhibition efficiency (IE) was found to increase with the increase in concentration of CTAB and it was also found that CTAB was effective only when used above a concentration of 100 mmol/L. Furthermore, the addition of 20 mmol/L of OPD to CTAB slightly increased the IE. The adsorption of these compounds on carbon steel in 1 mol/L HCl obeyed Langmuir's adsorption isotherm. These inhibitors reduced the permeation current. The IE was observed as high for 200 mmol/L of CTAB with 20 mmol/L of OPD in all the techniques studied. Scanning electron microscopy clearly showed that the inhibition was due to a polymolecular film formed by the physical adsorption of the inhibitor on the metal surface.Key words: carbon steel, corrosion, inhibitors, impedance, potentiodynamic polarization.