BS EN ISO 8502-6 describes a method of extracting, for analysis, soluble contaminants from a surface by use of flexible cells in the form of adhesive patches 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 is suitable for use in the field to determine the presence of soluble contaminants before painting or a similar treatment.
This part of BS EN ISO 8502 does not cover the subsequent analysis of the contaminants that have been dissolved off. Methods of analysis suitable for field use are described in other parts of the standard
The performance of protective coatings of paint and related products applied to steel is significantly affected by the state of the steel surface immediately prior to painting. The principal factors that are known to influence this performance are:
- The presence of rust and mill scale
- The presence of surface contaminants, including salts, dust, oils and greases
- The surface profile.
This is one of a number of parts of BS EN ISO 8502 that specify tests for the assessment of surface cleanliness. In connection with such tests, there are several methods for the extraction, for analysis, of soluble contaminants on surfaces to be painted. Some of these methods are based on the swabbing of comparatively large test surfaces. This technique provides average values of the contamination present, but it might conceal localized concentrations of contaminants. Also, swabbing might not ensure sufficient penetration to dissolve all of the deep-seated contamination such as ferrous salts.
There are other methods, however, which use small cells for the liquid used to remove and collect the surface contaminants. The cells (rigid or flexible) are attached to test surfaces where soluble contaminants could be expected, e.g. where pitting has occurred. This technique usually provides more accurate, point values of the contamination present.
BS EN ISO 8502 describes a simple, inexpensive field test using flexible cells in the form of adhesive patches designed to be filled with solvent. The method was originally developed by a Swedish scientist, Dr A Bresle.
