Multilayers of PAni/n-TiO2 and PAni on carbon steel and welded carbon steel for corrosion protection

Multilayers of polyaniline (PAni) and PAni/nanotubes-TiO2 composite were compared for corrosive protection on carbon steel and welded carbon steel. The layer porosity, morphology and thickness were characterized. PAni coating showed the best protection when a layer of 2 μm was deposited on steel surface. In spite of the good anticorrosive behaviour of PAni, when the layer thickness was increased up to 4.5 μm a decrease in the anticorrosive behaviour is detected due to the development of mechanical tensions which increase the porosity of the film. However, the addition of TiO2 nanotubes to PAni coatings shows an interesting ability to inhibit this undesirable mechanical effect, showing a good anticorrosive behaviour and lower porosity when thickness layer is increased. The morphological and electrochemical tests of the samples showed good resistance against degradation in chloride medium and in the salt spray analysis, promoting improvement of corrosion protection in an aggressive corrosion medium.