Written on: March 1, 2015 by W. Stephen Tait
Hello, everyone. Last month’s Corrosion Corner provided an overview of the relationship between spray package commercial life and spray package service life. These two lifetimes can be used to determine if corrosion is too severe to market a formula-package system or slow enough that failures will not be observed by consumers before the product is depleted and packages are recycled.
This month, I’m expanding the discussion of commercial life. Commercial life is the sum of several time periods:
Commercial life is influenced by the economy and the strength of the competition for individual products and product families. A strong economy usually means short commercial lives. A weak or volatile economy could increase commercial life. Competitive products could also lengthen commercial lives, particularly when competition is strong.
Figure 1 graphically illustrates a generic hypothetical model for commercial life. The Y-axis is the percent of spray containers from a given batch that are depleted and recycled at a given time. The X-axis is the spray package age when it is depleted. Commercial life in Figure 1 is defined as the time after filling when 100% of the packages are depleted and recycled.
Figure 2 has two hypothetical models for commercial life extremes. The left model (curve) portrays a strong economy with weak competition. The right model portrays a weak or volatile economy and/or when there is strong competition.
There could be a single manufacturing batch (lot) for small volume products as depicted in Figure 1. Presumably, large volume products would have multiple batches throughout a calendar year, as shown in Figure 3.
The hypothetical model in Figure 3 assumes new batches are manufactured for re-purchases when 50% of the filled packages from a previous batch are depleted and recycled. The model in Figure 3 also assumes that purchase-to-depletion time and commercial life do not change or fluctuate during the year.
Most likely, actual commercial lives are more complex than the model shown in Figure 3. Indeed, actual commercial lives are most likely a complex mixture of different models like those in Figure 2, particularly when there is a week or volatile economy and/or strong competition.
Corrosion is not an issue when service life is larger than commercial life. In most situations, spray package service life is less variable than commercial life. Next month, I will continue expanding the commercial and service life discussion with more details on the factors that determine spray package 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 April.
