Monolayers of n-pentanephosphonic acid grafted on aluminum substrates from ethanol and aqueous solutions are studied by X-ray photoelectron spectroscopy (XPS) and electrochemical techniques (polarization curves; scanning vibrating electrode technique, SVET; scanning Kelvin probe, SKP). The monolayers formed from the ethanolic solution are of better quality than those obtained from aqueous solutions, where dissolution of the oxide layer occurs. The cathodic inhibition of the samples modified in ethanol is also more effective, in accordance with the better coverage noted from XPS measurements. (C) 2002 Elsevier Science B.V. All rights reserved.