Adsorbtion of sodium tridecanoate on copper from aqueous solutions and copper protection from atmospheric corrosion

The adsorption and protective effect of sodium tridecanoate CH3(CH2)(11)COONa (NaC13) on copper and the possibility of increasing the effectiveness of protection by joint use with a trialkoxysilane (TAS) were investigated. A set of electrochemical, ellipsometric and corrosion tests was carried out on samples of M1 copper (copper content > 99.9%). From an analysis of the anodic polarization curves of copper from solutions containing NaC13, it follows that when the inhibitor concentration is > 0.07 mmol/l, the current density of copper active dissolution decreases and spontaneous passivation of the electrode occurs with a shift in the value of the pitting potential E-pit in the positive direction. With an increase in the concentration of the inhibitor, the value of E-pit increases while the anodic current density decreases. When the concentration of the inhibitor in the solution is 1.6 mmol/l or more, the value of E-pit shifts to the oxygen evolution region. Studies of NaC13 using the ellipsometric method showed that the adsorption of the inhibitor starts at very low concentrations, viz., 0.01 nmol/l. Adsorption is described by the Temkin equation with an adsorption free energy of 67 kJ/mol. In comparison with sodium oleyl sarcosinate CH3(CH2)(7)CH=CH(CH2)(7)CON(CH3)CH2COONa (SOS) and sodium laurate CH3(CH2)(10)COONa (NaC12), adsorption begins at lower concentrations. Sodium tridecanoate adsorption on copper is polymolecular. Accelerated corrosion tests with daily moisture condensation on copper pretreated with an inhibitor solution at 60 degrees C for 5 minutes were carried out. It was shown a protective mixture of NaC13 and TAS significantly increased the time until the appearance of the first corrosion site.