The Effect of Film Thickness and Substrate Resistivity on Corrosion of Fe Thin Films

Abstract

This study investigated the corrosion behavior of Fe films with different thickness in NaCl solution. It has been reported that nanocrystalline metal thin films are more corrosion resistant than their coarser or bulk counterparts, but the effect of thickness is not well characterized. Polarization curves were measured for three iron thin film with thicknesses of 10, 20, and 100 nm and bulk iron in aerated 3.5 wt% NaCl solution at 24 ˚C. Each film thickness was deposited on silica substrates, and 20 and 100 nm films were also deposited on silica substrates with a Pt conductive layer. The resistivity/conductivity of the samples were measured using four point resistivity measurement, and the effect of film and substrate resistivity on corrosion was addressed by comparing polarization curves of thin films with and without the platinum conduction layer. The extent of film corrosion was spatially varied and the variation in localized electrochemical response was measured using scanning vibrating electrode technique. The corroded films were also characterized by SEM.