Performance Of Maintenance Coatings Applied On Rusty Steel Surfaces

Presence of surface rust is normally assumed to decrease the performance of coatings. In this work various maintenance coatings were applied on pre-rusted steel cleaned by two different power tools: rotating disc and rotating steel brush. The rotating disc is much more efficient in removing rust than the rotating steel brush. The effect of cleaning method on the performance of the repair coating systems has been investigated. Surprisingly the rotating steel brush gave less corrosion creep than the rotating disc, in spite of the presence of an almost continuous film of rust on the steel brushed surface. Steel brushing removes less surface rust and salt contamination compared to the rotating disc, and rather poor results were therefore expected. The steel brushed samples had a surface quality corresponding to C St2, while the rotating disc gave a surface quality corresponding to C St3. Electrochemical characterization of cleaned panels showed a more positive corrosion potential for the steel brushed panels. This is probably due to a corrosion protection effect by the rust present on the surface of these samples.