Corrosion protection of carbon steel by alumina-titania ceramic coatings used for industrial applications

Alumina ceramic coatings containing 14 and 48 wt% TiO2 were thermally sprayed on carbon steel substrates by oxy-fuel using a neutral and oxidizing flame. The permeation of aggressive ions into these coatings was evaluated at different times and their protective behavior was compared with hard chromium coatings. The results showed that, in the first 24 h, the hard chromium coating was the most protective; however, its ability to protect the substrate substantially decreased after 7 days. On the other hand, a moderate performance was observed at 24 h for the alumina-14 wt% TiO2 coatings that were manufactured using the oxidizing flame, but after 7 days of exposure, these coatings displayed protective properties that exceeded those achieved by the hard chromium coating at 24 h. The other alumina-titania coatings behaved relatively weakly, most likely due to the ease with which the aggressive ions permeated through the pores and cracks of each coating.