Surface Cleanliness / Salt Detection

Salt Detection is a way of testing for Surface Cleanliness. Surface contamination from salts such as chlorides, sulphates and nitrates have been shown to lead to blistering of organic coatings, particularly in immersion conditions.

It is not sufficient to measure the cleanliness of the substrate. In a multi-layer coating process, it is necessary to monitor and record the cleanliness of each layer prior to applying the next coating.

When using amine cured epoxy coatings, for example, in low ambient temperatures or in high humidity, a surface oiliness or exudate may cause inter-coating adhesion failure.

Surface cleanliness: Soluble salts & ion specific contamination (sulphates, chlorides, nitrates etc.) which are often invisible to the eye, together with amine blush (for amine cured epoxy coatings) can result in premature coating failure, resulting in high re-coating and maintenance costs. Elcometer and BAMR have a range of test equipment for assessing surface cleanliness prior to applying a coating.

The type of tests can be split into:

• high up front costs and low cost per test.
  • The Elcometer 130 and the Soluble Salt Meter SSM are examples of these units
• relatively low up front costs but cost per test is high
  • The Elcometer 138 and the Elcometer 134 are examples of these