Written on: March 1, 2020 by W. Stephen Tait
Hello everyone. In February, I started a two-part discussion on whether or not corrosion testing is cost-effective. The objectives for corrosion tests—corrosion risks as a function of test time/completion—were discussed. I also mentioned that storage tests and electrochemical tests have several common parameters and that using inappropriate parameters invalidate results from both of these tests.
In this issue, I’ll complete the discussion with a few details on electrochemical corrosion testing and an example of how much an unexpected corrosion incidence might cost.
Not all types of electrochemical corrosion tests are the same
One can conclude that skipping corrosion tests and abbreviated corrosion tests are risky based on Figure 1.
Figure 1: The estimated risk of corrosion versus the percent test completion.
Electrochemical corrosion tests are completed in 1/4 of the time or less than the time needed to complete a corrosion storage test. Electrochemical tests are shorter because sensitive instruments are used to detect and measure corrosion instead of the human eye.
The risk associated for electrochemical corrosion tests in Figure 1 is less than 1%. This risk is based on the correlation for the proprietary Aristartec system, developed from two decades of direct comparisons between almost 1,000 tests and the corresponding actual corrosion for commercial spray packages.
I’m not aware of any correlations for other types of electrochemical corrosion tests. For example, the American Society for Testing & Materials (ASTM) procedures for electrochemical corrosion tests provide information about variability, but not correlations between predictions from the procedures and actual corrosion. Hence, the risk associated with other types of electrochemical tests is most likely higher than the Aristartec system, particularly when other tests use inappropriate test parameters and procedures.
What typically happens when unexpected corrosion results in spray package failure or significant product degradation and how much does the unexpected corrosion cost? Spray package failures typically trigger an internal company investigation into the failure. The objectives for an investigation typically include:
Failure investigations typically last from at least six months to one or more years, depending on the number of manufacturing batches involved and how widely the product was distributed. The investigation team typically includes people from all R&D disciplines and all levels of corporate management, as well personnel from manufacturing, quality assurance, legal, marketing, sales and customer service. Internal investigations typically involve numerous employees during the investigation lifetime—not usually all are involved at the same time.
Is skipping corrosion tests and/or abbreviated corrosion tests cost-effective?
The cumulative hours for a corrosion investigation typically add-up to a significant amount of time and cost. For example, an investigation might cost $180,000 if the investigation lasts one year and accumulates 1,200 hours of personnel time at a cost $150 per hour.
However, the loss of sales during the year, the cost of scrapped goods and consulting fees are not included in this example. In addition, an investigation also diverts resources from other projects, causing delays in commercialization of other products. Thus, the $180,000 in this example is probably significantly lower than actual the cost.
Unfortunately, costs could be much higher than in this example. Product recalls and litigation typically dwarf all other costs and are not included in my example. For example, my experience has been that warehouse/distributor recalls could cost many millions of U.S. dollars and an in-pantry recall could cost more than 10 million U.S. dollars, particularly if the recall also involves interfacing with government regulators. I’ve also been told by several litigation attorneys that failures associated with personal injury could cost at least $100 million. Consequently, recalls and litigation could be very expensive.
Therefore, the corrosion testing cost is insignificant when compared with the worst-case accumulative cost that could exceed $100 million. In other words, corrosion tests are very cost-effective.
To sum up…
Corrosion tests are cost-effective and skipping corrosion testing or abbreviated corrosion testing is not cost-effective. Corrosion testing lowers risk, reduces project delays caused by diverting resources to scrutinize failures and helps avoid costly investigations, recalls and litigation. Therefore, conducting corrosion tests to completion makes good financial sense.
Please visit www.pairodocspro.com for more information. Thanks for reading and I’ll see you in April. SPRAY
