Accelerated Corrosion Testing
These are used to give some idea as to the relative performance of different coatings. They are also used as a “quick” test for quality control purposes. (Though now some advanced coatings are lasting for 500-1500 hours in accelerated tests, they are not so quick!)
The most commonly used test is the 5% Neutral Salt Spray Test (to BS7479, ISO 3768 or ASTM B117). This test is used by most of the world for assessing the performance of many coatings (though not nickel chromium). See performance figures in Table below.
Other tests used include:
- A.S.S. – Acetic Acid Salt Spray BS 7479 ISO 3769.
- C.A.S.S. – Copper Accelerated Acetic Acid Salt Spray BS 7479, ISO3770. A fairly aggressive test used mostly for nickel chromium coatings.
- C.O.R.R. – Corrode Cote BS 7479, ISO 4541. Used as above.
- Kesternich – A test using sulphur dioxide.
Cyclic Tests (Climatic Tests)
To try to bring accelerated testing to give results more comparable with actual corrosion, many Original Equipment Manufacturers and other users have produced testing sequences which often use a combination of salt spray, humidity, drying periods, high (and sometimes low) temperatures. Parts are often subjected to a number of cycles. No standard test has yet been adopted but this situation is likely to change in the near future.
The usual failure point under accelerated testing is considered to be the first appearance of base metal corrosion (for zinc coatings, the appearance of white corrosion also has to be considered).
There is no correlation between the different accelerated tests and it is difficult to compare tests with actual performance in use, as the exposure in the environment varies considerably from place to place and year to year.
Approximate comparisons can be taken from the following table:
Information presented in this data sheet is considered reliable, but conditions and methods of use, which are beyond our control, may modify results. Before these product are used, the user should confirm their suitability. We cannot accept liability for any loss, injury or damage which may result from its use. We do not warranty the accuracy or completeness of any such information whether orally or in writing. We reserve the right at anytime and without notice to update or improve products and processes and our information concerning the same.
If you would like further information on corrosion testing from an industry expert or to find out how Anochrome can assist you, please email us via the Contact page, or alternatively you can call us on 01902 397333.