Anti-Corrosion Methods and Materials

Purpose – The purpose of this paper is to present the results of some corrosion inhibition studies of brass in 3N HNO3 by gemini surfactants.

Design/methodology/approach – Gemini surfactants namely: N-trimethyl butane-diyl-1,2-ethane-bis-ammonium bromide (BEAB), N-hexane-diyl-1,2-ethane-bis-ammonium bromide (HEAB), N-dodecane-diyl-1,2-ethane-bis-ammonium bromide (DDEAB) and N-hexadecane-diyl-1,2-ethane-bis-ammonium bromide (HDEAB) were synthesized in the laboratory and their influence has been investigated for controlling the dissolution of brass in 3N HNO3. Weight loss, potentiodynamic polarization and electrochemical impedance have been employed for the study. Weight loss experiments were performed as per standard method (ASTM, 1987). Potentiodynamic polarization studies were carried out using EG&G PARC potentiostat/galvanostat (model 173), universal programmer (model 175) and X-Y recorder (model RE 0089) and impedance measurements were carried out with an EG&G PAR (model 5301?A) lock-in-amplifier, using an IBM computer.

Findings – The inhibition efficiency for all the gemini surfactants increases with increase in concentrations. The maximum inhibition efficiency of each inhibitor was achieved at 250?ppm concentration. The inhibition efficiency of all the inhibitors decreases on increasing the temperature from 30 to 50°C. The results of potentiodynamic polarization studies revealed that all the compounds were mixed type inhibitors and inhibit the corrosion of brass by blocking the active sites of the metal. The adsorption of the compounds on brass surface in 3N HNO3 has been found to obey the Langmuir adsorption isotherm.

Originality/value – The paper provides information regarding corrosion inhibition of brass in 3N HNO3, the mechanism of the inhibition on the basis of molecular structures of the inhibitors, activation energy and free energy of adsorption.