The test standard summaries are for general guidance only. Though believed to be accurate at the time of writing, this may change over time. So this information should not be used as a substitute for referring to a complete test standard, at an appropriate revision level.
Note: the terms salt spray, salt mist & salt fog are all in wide spread use within corrosion test standards. In this context they can be considered to be equivalent and interchangeable terms.
Accelerated Corrosion Test (General Motors)
This is an accelerated laboratory corrosion test method that can be used to determine the corrosion resistance of automotive assemblies and components. It is said to be effective for evaluating a variety of corrosion mechanisms including general, galvanic, crevice etc. This test is cyclic in nature, i.e.; test specimens are exposed to changing climates over time.
Test specimens are placed in an enclosed chamber and exposed to a changing climate that generally comprises of the following 3 part repeating cycle (variations to this cycle are permitted depending on the type of component under test – refer to the full test standard for further guidance). 8.0 hours exposure to an ambient climate of 40 to 50%RH at +25C, during which salt solution is sprayed directly on to the test samples 4 times, for long enough to thoroughly wet them, and at intervals sufficient to allow the samples to dry between each spray. This is followed by 8.0 hours exposure to a water fog humidity climate of 100%RH at +49C. This is followed by 8.0 hours of air drying in a climate of <30%RH at +60C. The number of cycle repeats and therefore the test duration is variable.
This test is also referred to as a Cyclic Corrosion Test, often abbreviated to CCT.
For further information on General Motors standards visit; www.global.ihs.com