Polyethyleneimines (PEI) with different mean molar mass (from 1300 to 750,000 g mol(-1)) were studied as potential corrosion inhibitors for AISI 430 stainless steel in a 3% NaCl solution. Linear polarization measurements and immersion tests showed that all of the selected polymers protect this stainless steel against uniform corrosion. PEI with a mean molar mass of 2000 g mol(-1) provides the best protection against localized corrosion. as demonstrated by cyclic polarization measurements. A closer insight into the polymer adsorption was obtained by XPS technique. PEI molecules most probably physisorb on the metal surface since no peak shift was observed that would indicate C-N-metal connection. PEI probably acts as a diffusion barrier by preventing an attack by the chloride of the salt solution. (C) 2009 Elsevier B.V. All rights reserved.