Effects of Self-Assembled Monolayers on Cathodic Reactions at Stainless Steel Surface: Relevance to Localised Corrosion

Adsorption of lauryl phosphonic acid (LPA) on 316L stainless steel is shown to inhibit the cathodic reduction of Fe3+ in mild acid, but not that of O2. Progressively better inhibition of Fe3+ reduction with increasing LPA assembly time is observed, even though the LPA coverage appears from the surface wettability to saturate at short treatment times. This suggests that Fe3+ reduction is a sensitive probe of the degree of order in the LPA adlayer, not just its coverage of the passive surface.