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In the early 1990’s a group from the Society of Automotive Engineers (SAE) and the American Iron and Steel Institute (AISI) evaluated number of accelerated corrosion tests, they concluded that GM9540P provided the best prediction of cosmetic corrosion of cold rolled steel.
This study is a key reason why GM9540P became popular as an accelerated laboratory corrosion test for steel.
In recent years GM9540P has been replaced by its successor; GMW14872, but this is all but identical in terms of the test conditions required.
The GM9540P test is also referred to as a Cyclic Corrosion Test, often abbreviated to CCT.
The test consists of alternating wet and dry cycles with precisely prepared salt solution. NaCL, CaCL2 and NaHCO3 are utilised for the wet cycles with precisely controlled heat and humidity for the dry cycles.
Test specimens in the enclosed chamber are 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).
The number of cycle repeats and therefore the test duration is variable.
Originally developed by General Motors the standard has gained popularity for corrosion tests within the automotive industry and has also become the preferred corrosion test of the US Navy.