The self-assembly process of phosphoric acid mono-n-dodecyl ester (PMD) on cerium-based conversion coatings on galvanized steel has been investigated as an alternative to chromate conversion processes. Layer formation can be accomplished by an immersion of the coatings into a PMD solution. The results of contact angle measurements, infrared spectroscopy, and X-ray photoelectron spectroscopy show that the PMD molecules form a densely packed and crystalline-like self-assembled layer through the bonding between the phosphoric acid group of the PMD molecule and Ce3+ at the coating surface. Potentiodynamic polarization and salt spray tests revealed that the PMD layer significantly improved the corrosion resistance. (c) 2006 The Electrochemical Society.