Improving the corrosion protection of plasma electrolysis-treated light metal by polymeric functionalization

Abstract

Suppressing the rate of corrosive degradation has been the primary challenge in the widespread use of lightweight metals across a variety of potential applications because their native passive layer is still susceptible to chemical attacks in aqueous or humid environments. This work explores the roles of polyaniline in tandem with a TiO2 layer in improving the corrosion properties of pure Ti. The anodic TiO2 surface is a result of a plasma electrolysis treatment in a non-acidic, phosphate-based electrolyte. The emeraldine base form of the polymer is subsequently applied to modify the surface properties of the plasma-electrolyzed Ti samples to further protect the surface against polar species that might interact with TiO2. The deposition of the thin layer of polyaniline retains the original surface microstructure of the plasma electrolysis layer. Nevertheless, the presence of polyaniline successfully reduces the corrosion current density and passive current density of plasma-electrolyzed Ti by ~50%. The corrosion protection mechanism is explained in the context of equivalent circuit models based on impedance measurements.