This document specifies a method of extracting and analysing water-soluble contaminants from a surface by use of filter paper which can be attached to any surface, regardless of its shape (flat or curved) and its orientation (facing in any direction, including downwards).

The method described in this document is suitable for use in the field to determine the presence of water-soluble contaminants before painting or a similar treatment.

NOTE            The extraction method can give a false conductivity result or not take all the water-soluble material off the surface because of: (1) soluble materials hiding in the crevices or under folds of metal; (2) soluble materials under corrosion layers, passivation layers produced by corrosion inhibitors, oil, grease, or other non-visible thin films.