Applications
Comparative testing or 'ranking'
Because of its widespread use and long history, continuous salt spray testing provides a very useful method for undertaking comparative testing. This procedure is also known as 'ranking'. Such tests work on the basis of comparing actual corrosion rates with expected corrosion rates which are based on previous experience, in a practical application situation. For this reason continuous salt spray testing is most often carried out as a quality audit function to 'police' a production process, and passing or failing it, prior to the release of tested components to the next stage in the process.
For example; a manufacturer of anodised fasteners for the aerospace industry might regularly take samples of production items, and expose them to several hundred hours of salt spray testing under ASTM B117, in order to verify the anodising process is operating within acceptable limits.
Automotive component manufacturers will do likewise for plated or painted automotive components. The duration of these tests generally reflects the item's location on the vehicle such that the test is representative of the exposure to corrosive effects likely to be experienced by the component in its service life.
In order that the testing is as representative of the actual service situation as possible, most manufacturers of 'products' who do such testing, will generally test the actual item, or a sample section of it, rather than use a test panel which might provide less representative results. However, the use of actual components can present some challenges in terms of how to support these items whilst under test.
