The reference system without PANI is a white paint (TiO2 and
CaCO3 pigments) while the coating with PANI all exhibit a graygreen
color, characteristic of the ES state of PANI.
The more intense green color was obtained with the more conductive PANI, i.e., PANI–LS1.
The initial gray-green color gradually turned to a gray blue
color during corrosion tests (salt spray and immersion in NaCl solution).
This suggests that ES de-protonate to EB during testing, as
reported before for PANI primers [32]. Previous studies have shown
the stability of the ES state up to pH 4 for conventional HCl-doped (1.5% and 3% of PANI–BS).
No or only few small blisters and rust spots were observed on coatings containing 0.5% PANI–BS, 1.5% or
3% PANI–LS1 and 3% PANI–LS2.
Visual observations thus confirm again that the best anticorrosion properties are obtained at low
loadings (0.5%) of PANI- with BS dopant and high loadings (1.5 or 3%) of PANI with LS dopant.