Polarization measurements were employed, as a first step towards studying the corrosion behaviour of Al and two Al-Cu alloys, namely Al-4.5%Cu, and Al-7.5%Cu alloys in deaerated stirred 1.0 M H3PO4 solution at 25 A degrees C. Inhibition of Al and Al-Cu alloys corrosion in 1.0 M H3PO4 solution, using sodium oleate (SO) as an anionic surfactant inhibitor, was also studied. Polarization curves showed that SO acted as a mixed-type inhibitor to Al corrosion, while it acted mainly as a cathodic inhibitor to the acid corrosion of Al-4.5%Cu, and Al-7.5%Cu alloys. Inhibition is accomplished by inhibitor adsorption on the electrode surface without detectable changes in the chemistry of corrosion. The relationship between surfactant concentration, surfactant critical micellar concentration (CMC), and corrosion inhibition is also discussed based on the Langmuir isotherm assumption, commonly applied in corrosion inhibition evaluations. The protection efficiency increases with increase in surfactant concentration and %Cu in Al samples. Maximum protection efficiency of the surfactant is observed at concentrations around its CMC. The mechanism of adsorption is discussed based on the surface charge of the electrode surface.