scope:

General

Numerical Salt Level Values

The assessment and determination of surface contamination (by salts) prior to application of protective coatings can be critical to estimating and attaining the desired service life of the coating system in a given environment.

Application of protective coatings over salt contamination may cause degradation of the coating system and substrate. This may lead to breakdown of the corrosion protection provided by the coating system. These effects can reduce the expected service life of the coating.

It is the intent of this standard to provide a set of defined salt levels that can be used by the industry. In any given environment, salts are usually present on surfaces to some degree. It is not the intent of this standard to provide guidance to the industry on how to mitigate soluble salt contamination.

This standard does not suggest what level of salt is acceptable in any given application. It provides a set of defined soluble salt values currently utilized in the marketplace. The user may use these to specify surface cleanliness requirements before coating.

Determining Numerical Surface Salt Values

Numerical determination of the quantity (level, in accordance with Table 1) of surface nonvisible soluble salt shall be performed using a field method for the conductometric determination of water-soluble salts in accordance with ISO(1) 8502-91 or an equivalent method as determined by NACE SP0508.³ The "Bresle method" for extraction of soluble salt contaminants is performed in accordance with ISO 8502-6.² The field execution of ISO 8502-6 involves using a syringe to inject deionized water into the Bresle patch, washing the substrate surface inside the patch, then extracting the test water for direct measurement of conductivity. Details of this procedure are provided in Appendix A (mandatory). Once a conductivity value is determined by the conductivity meter, expressed as microsiemens per centimeter (μS/cm), ISO 8502-9 provides a procedure to calculate the NaCl equivalent weight of the surface concentration as total surface density of the salts (in mg/m²).

It is not the intent of this standard to preclude measurement of soluble salt contamination by other methods as long as the values generated are equivalent to those generated by ISO 8502-9. Any equivalent tools, methods, or procedures must demonstrate they meet the criteria defined in NACE SP0508.

⁽²⁾ Standards Norway, Srandvein 18, P.O. Box 242, N-1326, Lysaker, Norway.