higher temperatures to accelerate package material corrosion is technically invalid and the risk curve in Figure 1 cannot be used for this situation. In other words, a storage test conducted for only three months at 40°C is not equivalent to six months of room temperature testing (20°C); the risk for the higher temperature data has the same risk after three months of testing. In addition, examining one or two package samples for corrosion has an approximately 0% statistical confidence (~100% statistical risk) and examining three packages has an approximately 55% statistical confidence (~45% statistical risk). Consequently, examining a low number of packages after a short exposure time at a higher temperature has a high corrosion risk. Let’s move on and discuss the correlations for electrochemical corrosion tests. Notice in Figure 1 that the corrosion risk for electrochemical tests reaches its lowest magnitude after 30 days of testing on uncoated spray packages and 90 days of testing on coated and laminated spray packages. Notice also that the risk with electrochemical testing is less than 1% (or greater than 99% confidence) for both types of electrochemical tests. A word-of-caution about Figure 1 for electrochemical tests: the two correlations were generated with specific test protocols and instruments. Thus, the correlations (risks) in Figure 1 are not valid for all electrochemical corrosion test protocols and instruments. Consequently, data from other instruments and test protocols could have significantly higher risks than those in Figure 1. In summary, Figure 1 illustrates that: • It takes one year of storage testing to obtain an approximately 7% risk of localized corrosion in traditional aerosol containers (e.g., metal pitting and coating blistering) • It takes 90 days or less of electrochemical corrosion testing to obtain a risk of localized corrosion that is less than 1% • In other words, you have a significantly lower risk after a much shorter test time with electrochemical corrosion tests. We would be happy to teach our Elements of Spray Package (Aerosol Container) Corrosion short course, which provides a more comprehensive discussion on spray package corrosion science and technology, corrosion prevention and control, at your R&D facility. We have also introduced the Corrosion Partnership Program, which makes our electrochemical corrosion laboratory, corrosion consulting and anti-corrosion technology conveniently available for your R&D program. Contact: rustdr@pairodocspro.com; 608-831-2076; www.pairodocspro.com. Back articles of Corrosion Corner are available from Spray. Thanks for your interest and I’ll see you in March. Spray February 2017 Spray 23 FORMULATE CREATE Formulated Solutions offers the most streamlined turnkey Concept-to-Consumer CDMO solution in the industry. Specializing exclusively in Consumer Healthcare, Rx, OTC, Medical Device, Aerosol, BOV Aerosol and Semi-Solid manufacturing. Visit our website: www.formsol.com Sales Inquiry: websales@formsol.com Phone: 727-373-3970 INNOVATE Aerosols and Foams • Pressurized Container Systems - Bag-On-Valve Airless & Metered-Dose • Plastic, Laminate and Metal Tubes Wipes & Sachets • Semi-Solids, Liquids, Pastes and Gels
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