Octadecylphosphonic Acid Self-Assembled Monolayers as Lubricant Coatings Stable in Alkaline Media

The formation of octadecylphosphonic acid self-assembled monolayers (SAMs) on titanium deposited by cathodic sputtering on planar substrates has been studied by water contact angle measurements and Atomic Force Microscopy (AFM). Dense monolayers were obtained after one week of reaction. Tribological experiments indicated that these monolayers had good lubricating properties, which were maintained after immersion in a 1 M NaOH solution at 65 °C for up to 100 min. The stability in alkaline media of octadecylphosphonic acid SAMs on titanium was ascribed to the high chemical stability of Ti-O-P interfacial bonds.