Resistance to water is perhaps the most important coating characteristic since all coatings will come in contact with moisture in one form or another and the water molecule is an extremely small one with the ability to penetrate into and through almost all organic compounds.  Knowledge on how a coating resists water immersion is helpful in predicting its service life.  There are a number of factors that may cause coating failures in a water immersion test, including a deficiency in the coating itself, contamination of the substrate, or inadequate surface preparation.

The Hot Water Immersion test, also named as Soak Adhesion test and Wet Adhesion test, examines a coating’s ability to adequately protect the steel substrate from water immersion conditions.  The test involves fully immersing the coated steel panels in tap water at the required test temperature for the required duration and then assessing the adhesion of the coating by scribing a rectangle approximately 30 mm x 15 mm through the coating to steel substrate in the center of each test panel and applying a levering action to remove the coating within the rectangle with a utility knife.


A Plus Coating’s Hot Water Immersion Apparatus


Test method for the Hot Water Immersion is available in:

  • CSA Z245.20, Section 12.14
  • NACE SP0394, Appendix J
  • API RP 5L7, Appendix 16
  • API RP 5L9, Appendix L
  • ISO 21809-1, Annex M
  • ISO 21809-2, Annex A.16
  • ISO 21809-3, Annex I
  • BS EN 10289, Annex G
  • BS EN 10290, Annex G

Test Samples:

   Typical specimens consist of 4″×4″ coated panel