The presence of water-soluble contaminants (particularly sulphates and chlorides) at the steel/paint interface is known to have detrimental effects on the performance of most paint systems. In this paper an assessment is presented of the residual contamination left on rusty steel after brushing and once the steel had been exposed to a broad range of atmospheric conditions. Also an attempt has been made to relate that residual contamination with the aggresiveness of the atmosphere according to International Standards Organization Standard (ISO 9223).