Fabricating protective epoxy-silica/CeO2 films for steel: Correlating physical barrier properties with material content

Publication date: 15 June 2017
Source:Materials & Design, Volume 124
Author(s): Ubong Eduok, Omar Faye, Ahmed Tiamiyu, Jerzy Szpunar
Upon the numerous researches on material protection, less attention has been drawn to the in-depth studies of the failure mechanisms accompanying modified organic coating formulations and their inherent barrier properties. In our present study, the mechanism for failed barrier properties of a new epoxy-silica polymer coating designed to anchor CeO2 pigments has been proposed while also investigating the impact of content leaching on the microstructure of coated metal substrate. By deploying a rare earth content in CeO2 pigments within its sol-gel network, we have observed improved protection against steel corrosion in an aerated corrosive medium by electrochemical impedance spectroscopy. Though protective performance increased with CeO2 content, beyond 1wt% concentration, the coating network becomes saturated with inorganic pigments thereby widening conducting paths for the flow of ionic currents towards the metal surface via the coating. These excess CeO2 contents tend to assume uneven distribution patterns within the sol-gel network leading to coating disbonding. The failed protective abilities of this modified sol-gel type coating design has been linked with particulate leaching upon prolonged exposure; evidence of this assertion has been established by SEM analyses though AFM evidence also reveals significant coating disbonding without these pigments.

Graphical abstract

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