It was concluded that the anticorrosion
efficiency of the organic coating with this pigment was highest at
PVC = 2% and 3%.
The organic coatings with PANI-CAS as the pigment attained
a high anticorrosion efficiency at PVC = 0.1–2%. Corrosion on the
panel surface was ≤0.3%and corrosion in the cut was 0.5–1 mm. The
occurrence of blisters on the panel surface at these PVC levels was
lower than for the non-pigmented organic coating. The anticorrosion
efficiency, however, decreased at PVC > 3% and became poorer
with increasing PVC. None of the organic coatings attained anticorrosion
efficiency as high as that exhibited by the non-pigmented
organic coating. It follows from the above results that presence of the conductive
polyaniline compound in the organic coating brings about
increased anticorrosion resistance if the PVC is kept adequately
low, but this effect is reduced at high PVC levels. The latter phenomenon
can be explained in terms of a decrease in the barrier
effect in the organic coating with a high conductive polyaniline
compound content. This is associated with increased permeability
of the organic coating for the aggressive environment, resulting
in a rapid attack on the initially protected substrate. This fact has
also been reported in other publications devoted to the anticorrosion
efficiency of conductive polyaniline compounds [30]. The
PVC, however, is not the sole parameter affecting the anticorrosion
efficiency of an organic coating; the type of the dopant present
in the conductive polyaniline compound is an important factor as
well.
Fig. 3 shows organic coating and a steel panel after 1440 h of
exposure in a salt mist atmosphere.
The results of the tests examining the resistance of these organic
coatings to an atmosphere with SO2 are summarised in Table 5.
The exposure time was 2208 h. Four types of corrosion effects,
appearing to different extents depending on the PVC as well as on
the dopant type, were examined.The organic coatings with PANI-H3PO4 as the pigment attained
a high anticorrosion efficiency at PVC = 0.1–5%. Corrosion on the
panel surface was ≤1% and corrosion in the cut was 4–4.5