The formation of a protective layer by dipping copper specimens in a hydroalcoholic solution of a silanic agent with a long aliphatic chain (n-octadecyl-trimethoxy-silane, OctadecS) was studied using electrochemical techniques (impedance spectroscopy and potentiodynamic polarization curve) and FTIR spectroscopy. By simple immersion, the protective effects of OctadecS film are poor. Aging, and particularly curing improves its inhibiting performance. The latter treatment produces a thicker and more persistent, and therefore, more protective silanic layer. The interactions between the long aliphatic chains of OctadecS molecules as well as the condensation of their silanol groups are considered in relation to the formation of a thick and efficient silanic coating. (c) 2007 Elsevier B.V. All rights reserved.