1999 Volume 48 Issue 9 Pages 575-582
Protection of carbon steel (C-steel) from atmospheric corrosion by TiO2 coating was demonstrated. TiO2 coating, as a non-sacrificial anode, absorbed solar energy and transformed it to electricity so as to provide cathodic protection to the substrate steel. A TiO2-Fe galvanic couple was developed as an ACM (atmospheric corrosion monitor) sensor to evaluate the photoeffect and corrosion behavior of TiO2/C-steel in atmosphere. For the TiO2-Fe couple, type 1 sensor, an anodic output related to the anodic dissolution of the coupled Fe electrode was detected in the dark (night time), whereas in the bright (day time) the output changed from anodic to cathodic. Moreover, the cathodic output remained for a long time after stopping illumination for the multi-layer coating, TiO2 (amorphous)/TiO2 (anatase)/Ti-Fe oxide/α-Fe2O3/C-steel, type 2 sensor. Enviromental conditions in terms of relative humidity, RH, and amount of deposited sea salt, Ws, where 1mm wide Fe coupled to 5mm wide TiO2 could be protected were determined based on the following examinations:
a) visual observation for degree of rust developed on the Fe electrodes, for the type 2 sensor
b) comparison of corrosion potential of carbon steel with photo potential of TiO2 electrode measured by Kelvin probe,
c) polarity of output current for the type 1 sensor.
It is concluded that the carbon steel could be protected from atmospheric corrosion by TiO2 coating under conditions of lower amount of deposited sea salt and lower relative humidities.