PAni based composite was synthesized, and the effect of n-TiO2 on the coating was analysed,
comparing its behaviour with that of the PAni coating. PAni/n-TiO2 was found to be a good
adherent and anti-corrosive coating. An increase in the adhesion and anticorrosive behaviour
was detected when the thickness coatings increased, thereby reducing the porosity of the
coating. The improvement with respect to the PAni coating resulted from increased adhesion to
the steel surface and hence the increased durability of the coating. The good adherent properties
are due to the nucleation process during the synthesis, where the n-TiO2 acts as seed for the
polymerization of PAni, decreasing the stress and increasing the adhesion when multiple layers
are deposited on the steel. The use of the PAni/n-TiO2 coating on the welded carbon steel
demonstrated that this layer is protective against corrosion on welded material
The anticorrosive behaviour of PAni-1 and PAni/n-TiO2-1 coatings were determined using
polarization curves in 3% sodium chloride medium. Figure 4a electrochemical polarization of
the coatings compared with bare steel. Both coatings present anticorrosive behaviour compared
with bare steel, being the more protective coating PAni-1, which present the lower current
density and a Ecorr close to zero. From these electrochemical meassurements the coating
porosity can be determined from relation (1), table I summarize the electrochemical parameters
and the porosity determine for each coating. As can be presented in table I, the good
anticorrosive properties of PAni coating is related with its lower porosity, indicating that PAni
coating shows a more compact structure than PAni/n-TiO2, where the polluted electrolyte can
penetrate through the coating and start the pitting corrosion process. After the electrochemical
tests, the coatings were removed, (using adhesive tape to remove the coating) and the steel