As proved inhibitor of copper corrosion in saline environment, the white willow bark (WWB) extract was characterized using the Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) method. By identifying the bands typical for phenolic profile of WWB extract, the anti-corrodic properties of WWB were explained. The hydrogen-bonded O-H stretching vibrations present in WWB extract is attributed to the phenolic hydroxyl groups and alcoholic hydroxyl groups within glycosides. The C-H stretching vibrations typical for salicin and for glucoside part of salicin aromatic were also identified, as well as the C=C ring stretching vibrations and C-O stretching vibrations that can be attributed to phenolic and alcoholic groups. The presence of these functional groups confirms the presence of a protective film of the WWB extract on the copper surface, protecting the metal from the corrosive effect of chloride ions.