Written on: October 1, 2020 by W. Stephen Tait
Hello, everyone. The global COVID-19 pandemic has had a significant negative impact on sales of consumer packaged goods. In an ideal world, spray products could be stored indefinitely in warehouses during an economic slowdown/stoppage and then sold when the economy rebounds or restarts.
However, all packaging has a service lifetime, after which failures begin to occur. Spray package failure is defined as one or more events that occur after a spray package is filled, including:
• Non-spraying
• Degraded product efficacy
• Leaking product or propellant
Consequently, filled-package service lifetime (PSL) is the length of time prior to when packages leak from pin-hole corrosion, no longer spray because of lost propellant or clogged valves or have degraded product efficacy caused by corrosion. In other words, the PSL is the amount of time during which a spray packageformula system sprays, is efficacious and does not leak product or propellant.
PSL magnitudes are different for each type of formula-package system and should be determined with either long-term storage stability tests (at least one year) or shorter electrochemical corrosion tests employing the appropriate measurement parameters.
There are situations where the actual PSL is longer than the specified PSL. The product is most likely sellable for a limited additional amount of time beyond the specified PSL in these situations. Of course, the amount of additional time needs to be determined.
There are also situations where the actual PSL and the specified PSL are the same. Packages are close to failure when their age is close to or exceeds the specified PSL in these situations.
Is there a standard maximum PSL for spray products? The short answer is No! Maximum PSL is determined by the type of product and package materials along with a product’s chemical composition. However, some general PSL guidelines are:
• Five or more years for food and pharmaceutical products
• Three years for seasonal products (which could include insect control, lawn care and sun care products)
• Two years for all other types of spray products
Please keep in mind that these PSL numbers are not standards. Your company might have higher or lower target PSLs than those listed above.
Why be concerned with PSL & older products in a warehouse?
PSL might not be a constant with age, particularly when a product’s chemical composition changes with age. For example, the product pH in a filled package might drift with increasing product age, or an active ingredient might decompose with increasing age. Metal ion contamination from very low general corrosion might eventually degrade product efficacy as the age of the filled-package approaches its PSL (e.g., detinning and slight corrosion in steel and aluminum aerosol containers).
Formula chemical composition changes due to age might also make a product corrosive, even though it was not corrosive during the specified PSL. In addition, the corrosive version of an older product might induce very rapid metal pitting corrosion that causes leaking very shortly after the specified PSL. In other words, even though the pitting corrosion initiates after a long time, it could be very fast and cause package leakage very shortly after the specified PSL. Consequently, older spray products could lose enough propellant to stop spraying and/or could leak. In both cases the products are no longer sellable.
An audit is in order…
Has the pandemic caused your spray product ages to approach their specified PSL? Should older products be scrapped or are they still sellable? No one would sell products that would fail; and why scrap products that are safe, efficacious and have sufficient remaining PSL?
Hence, a corrosion audit is recommended for older spray products whose ages are approaching, or have exceeded, their specified PSL. A comprehensive audit on older spray products in warehouses would, at the very least, include:
• Estimating the amount of remaining service life for older filled packages
• Assessing product efficacy in older packages that have corrosion
• Assaying active ingredient potencies to make sure they meet specification in older packages
• Spraying a number of samples until they no longer discharge, to determine if there is sufficient propellant to deliver the full label amount
• Estimating the number of packages with clogged valves
Multiple samples from all manufacturing batches (lots) should also be evaluated whenever older spray product stock consists of several manufacturing batches.
Like many of you, I’ve been through several economic downturns during my 40+ years of corrosion research and engineering. Previous comprehensive audits on older spray products in warehouses helped avoid expensive recalls and scrapping products that are safe, efficacious and sellable.
Pair O Docs has developed a web version of its Elements of Spray Package Corrosion course in response to the COVID-19 pandemic. The course is offered for 5–30 participants, enables team members to participate from any location and costs less than the on-site version. Call 608-831-2076 or email rustdr@pairodocspro.com for more information. Thanks for reading and I’ll see you in November. SPRAY
