Pitting Corrosion of Aluminum in Aqueous Solution with Low pH Containing Nitrate Ion and Its Inhibition Using Different Surfactants

Localized or pitting corrosion of aluminum in acidic medium is a problem for some industries. Severe attack can lead to pinhole leaks and instrument breakdown. The results showed that pitting corrosion occurred in waters with low nitrate ion concentration. The effect of adding different types of surfactants on the inhibition of the pitting corrosion of aluminum in 0.1 M HNO₃ was studied using potentiodynamic polarization and electrochemical impedance (EIS) spectroscopy techniques. The electrochemical results proofed that both the anionic surfactant sodium lauryl sulfate and the cationic surfactant cetrimide can decrease the pitting corrosion of aluminum in aqueous solution containing nitrate ion to a great extent. The mechanism of adsorption of surfactants on metal surface was studied using the kinetic thermodynamic model. The free energy change of adsorption indicated that the adsorption of surfactants on metal surface is spontaneous in nature. The adsorption of both surfactants is comprehensive process (physical and chemical)