From Food Preservation to Surface Protection: Enhanced Corrosion Protection by Fatty Acid Salts

The ability of dissolved monocarboxylate salts, often used as food preservatives, to produce surface passivation and to inhibit aqueous corrosion of metals and alloys is discussed. Electrochemical measurements indicate that the inhibiting efficiency of these compounds, with a general formula Cn-1H2n-1COOK or CnK (n = 3...12), is dependent on the hydrocarbon chain length. Inhibiting efficiency was higher for a longer hydrocarbon chain of n-alkanoic acid. Copper corrosion protection level was found to increase with an increase in fatty acid salt concentration the optimum concentration of potassium dodecanoate (C12K) in sulfate solutions was found to be 70 mM. Protective layers formed at the copper surface Subsequent to exposure in various n-alkanoate solutions were characterized by all electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared reflection spectroscopy, and contact angle measurements. Observed copper passivation is attributed to the growth of a protective film oil the copper surface, containing both copper oxides and copper carboxylate compounds. The organic molecules enhance copper protection by covering copper oxides with a thin and dense organic layer, which prevents water molecules or aggressive anions from interacting with the copper Surface.