For BS as a dopant, a
low loading of PANI, i.e., 0.5%, gives the best inhibitive properties.
An opposite trend is observed with the LS dopants, especially with
PANI–LS2. The coatings with 0.5% PANI–BS, 1.5% PANI–LS1 and 3%
PANI–LS2 all show about the same protective efficiency: the current
density at Ecorr for the steel coated with these coatings was
decreased by about two orders of magnitude as compared to the
steel coated with the paint without 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 grayblue
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 Previous studies have shown
the stability of the ES state up to pH 4 for conventional HCl-doped
PANI [33] and pH 7–8 for a PANI obtained in aqueous micellar system
mediated by sodium dodecylsulfate