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Spray Feb 2015

February 2015 Spray 27 In this example, the corrosion is very slow and empty packages are in the recycling stream long before container failures are expected to begin (failure is leaking or non-spraying). Thus, package corrosion in this example does not present a problem, as long as the economy doesn’t cause the commercial life to become longer than the service life. Figure 3 illustrates a situation where the commercial life is longer than the service life. This type of situation typically occurs when the corrosion rate is large. The vertical dashed line in Figure 3 shows that approximately 70% of the containers from a given manufacturing batch are exhausted and recycled after approximately 1.25 time units. In other words, approximately 30% of the filled containers at this time are still full and a fraction of the consumers would probably have packages that either leak or do not spray. The magnitude of the fraction could be low or high. The corrosion illustrated in Figure 3 should be addressed before the product-package system is ready for introduction into the marketplace. The situation in Figure 3 also illustrates how a large difference between service life and commercial life is desirable to avoid unwanted surprise failures caused by package variability, product chemical composition variability or economic fluctuations. Next month, I’ll continue this discussion with more detail about the factors that determine the magnitudes of commercial life and service life. 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. Want a specific topic discussed in an issue of Corrosion Corner? Please send your suggestion/ questions/comments to rustdr@pairodocspro.com. Back articles of Corrosion Corner are available from Spray. Thanks for your interest and I’ll see you in March. SPRAY


Spray Feb 2015
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