TWI Frequently asked questions
Coating corrosion performance can be evaluated while the coating is subjected to a corrosive atmosphere. One approach is to use a salt spray test in which a corrosive solution is atomised onto the test piece in an enclosed chamber.The salt spray solution can be neutral or modified to be more acidic for example.
An alternative approach is the saline droplet corrosion test, where a pattern of discrete droplets of a specified test solution are placed on the surfaces being tested. The test specimen is stored in conditions of high humidity, andthe test solution reapplied only when it is needed to maintain the pattern of droplets.
Some standards relative to corrosion testing in a corrosive atmosphere are:
- ASTM B117: Standard practice for operating salt spray (fog) apparatus
- ASTM G85: Standard practice for modified salt spray (fog) testing
- EN ISO 4536: 1995 Metallic and non-organic coatings on metallic substrates - Saline droplets corrosion test (SD test)
- EN ISO 4538: 1995 Metallic coatings. Thioacetamide corrosion test (TAA test)
- EN ISO 4540: 1995 Metallic coatings. Coatings cathodic to the substrate. Rating of electroplated test specimens subjected to corrosion tests
- EN ISO 4541: 1994 Metallic and other non-organic coatings. Corrodkote test (CORR test)
- EN ISO 6988: 1994 Metallic and other non-organic coatings. Sulfur dioxide test with general condensation of moisture
- EN ISO 8403: 1995 metallic coatings. Coatings anodic to the substrate. Rating of test specimens subjected to corrosion tests
- ISO 9227: 1990 Method for salt spray corrosion tests in artificial atmospheres
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