PAINT TESTING

A great amount of financial losses are incurred every year as a result of untimely failure of paints and coatings. Costs of such failures far outweigh the initial costs of painting because of the complexity of repairs and the liability associated with downtime to correct the problems.

SALT SPRAY TEST -

The Salt Spray test is a standardized test method used to check corrosion resistance of coated samples. Frequently the tests are used to test the protective coatings applied to metallic substrates.  Salt spray test is also called as Fog Test. Salt spray test is an accelerated environmental corrosion test that produces a corrosive attack to the coated samples in order to predict its suitability in use as a protective finish. In this test, metal specimens are exposed either continuously or intermittently to a fine mist of salt-water solution used to evaluate the resistance to corrosion of paints, coatings, or electrical connections. The appearance of corrosion products (oxides) is evaluated after a period of time. Test duration depends on the corrosion resistance of the coating; the more corrosion resistant the coating is, the longer the period in testing without showing signs of corrosion. Parts or panels are placed inside a chamber and exposed continually for a specified period then evaluated for resistance to rust.

The tests are performed in a controlled corrosive environment designed to represent marine type atmospheric conditions. The results are accelerated by the test temperature, the test solution, the degree of wetness etc.

Salt spray testing is popular because it is cheap, quick, well standardized and reasonably repeatable. There is, however, no direct correlation between the test duration and the expected service life, since corrosion is a very complicated process and can be influenced by many external factors. Despite this, salt spray testing is widely used in industry for the evaluation of corrosion resistance of finished surfaces or parts in order to predict relative suitability for use in service or as a quality control test.

A significant amount of salt spray testing involves the evaluation of coatings using standardized test panels. The paint/coating test panels can also be evaluated after exposure for "creep", blistering, rust, etc. using standardized ASTM and related specifications or specific customer performance requirements.

Materials Technology offer the neutral salt spray test (NSS) as standard, which is perhaps the most commonly used salt spray test, and is performed with a solution of NaCl (typically 5%) at a neutral pH between 6.5 & 7.2. The duration of the test can range significantly, but will typically run from 500-1000 hours.