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Spray Dec 2014

December 2014 Spray 43 Periodic inspections of commercial packages help to ensure that variability does not cause the inhibitor to lose its effectiveness and the service life to decrease below the target length. A comprehensive corrosion control and prevention program includes corrosion testing prior to commercialization of the product. There are two general categories of corrosion tests for spray packaging: storage stability tests and electrochemical corrosion tests. Storage test data can be used to estimate service lifetimes, and thus provide information for decisions on the suitability of a product-package system for a commercial market. Electrochemical corrosion test data can also be used to estimate service lifetimes with the appropriate empirical models. Good practices for stability tests should: • include periodic destructive inspections of test samples for internal package and valve corrosion (for example, inspections every three or four months) • have replicate package samples examined at each inspection interval (more than three packages) • use high temperature test conditions for product thermal stability determination and not to accelerate corrosion • be conducted for at least one year before commercialization decisions are made Electrochemical tests are shorter than storage tests because the instruments used for detecting corrosion are more sensitive than the human eye and a light microscope. The correlation between electrochemical results and actual corrosion are very high when the appropriate test parameters are used for the measurements (in excess of 99%). Sometimes products are abandoned during development because corrosion was found in storage stability tests. However, it has been my experience that corrosion does not always indicate that a product should be abandoned. Indeed, I prefer to think that the development timetable needs to be extended when corrosion is found. My preference is for prevention. However, individual companies must decide whether corrosion control or corrosion prevention is appropriate for a given commercial spray product. We would be happy to teach our Elements of Spray Package (Aerosol Container) Corrosion short course at your R&D facility. Contact rustdr@pairodocspro.com or visit www.pairodocspro.com. Please send your questions/comments/suggestions to rustdr@pairodocspro.com. Back articles of Corrosion Corner are available from Spray. Thanks for your interest and I’ll see you in January. SPRAY


Spray Dec 2014
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