Corrosion behavior of plasma electrolysis layer cross-linked with a conductive polymer coating
M.P. Kamil, Tri Suhartono, Young Gun Ko
Abstract
Tackling corrosion issues by oxide coatings has been one of the key research issues in valve metals, but these oxides are chemically vulnerable to a degradative hydration process in an aggressive environment. In this work, we highlight the role of poly3,4-ethylenedioxythiophene-polystyrenesulfunate (PEDOT:PSS) in tandem with TiO2 anodically grown by plasma electrolytic oxidation on pure Ti substrate. The addition of 1–10 wt.% citric acid as cross-linking agent enables PEDOT:PSS to work properly as a protective coating under aqueous conditions. We found that excessive amounts of citric acid led to the formation of micro- and nano-scale clusters of PEDOT:PSS on TiO2 surface, which are detrimental to the barrier effect against the corrosive medium. Thus, polarization and impedance test results suggested that the use of 1 wt.% of citric acid resulted in PEDOT:[email protected]2 layer with superior corrosion resistance. Furthermore, analysis of space charge capacitance reveals a decrease in the donor density, as calculated from Mott–Schottky plot of PEDOT:[email protected]2, pertaining to its passivation effect against ion and electron diffusion.