W. Stephen Tait, Ph.D. Corrosion Corner Corrosion prevention and control is a process, not a one-time event. Chief Science Officer & Principal Consultant, Pair O Docs Professionals, LLC for an existing successful, non-corrosive formula is extended by adding more fragrances to a base formula. However, one or more of the derivative formulas turn out to be corrosive (base formula with new fragrances). In this type of situation, it’s typically not that the fragrance is corrosive. Instead, one or more of the new fragrances are not as effective at inhibiting corrosion as the original fragrance. In other words, the unfragranced formula base is actually corrosive. Corrosion can unexpectedly appear with changes in the concentrations of formula ingredients either by design or by manufacturing batch-to-batch variations. Corrosion inhibitors have an effective concentration range above which the inhibitor no longer effectively controls or prevents corrosion and below which the inhibitor no longer effectively controls or prevents corrosion. Thus, corrosion inhibitor concentration variations actually cause corrosion, particularly when the effective concentration range is small. Substituting formula ingredients from alternate suppliers could also cause unexpected corrosion in spray packaging. Additionally, contamination, such as water in anhydrous formulas, is a common cause for spray package corrosion. What are the elements of an effective and comprehensive corrosion prevention and control program? A comprehensive corrosion control and prevention program consists of several elements as illustrated in Figure 2. A brief overview for each of the elements in Figure 2 is: • Corrosion testing is used to determine package-formula compatibility • The most corrosion-resistant forms of packaging components are selected with corrosion tests • Coatings for spray package components are selected with corrosion tests • The most effective corrosion inhibitor and its effective concentration range are selected and determined with corrosion tests Hello, everyone. In the May–July 2016 Corrosion Corners, I discussed corrosion risk and how the cost for corrosion failures is significantly higher than corrosion testing. Corrosion prevention and control is a continuous process and not a one-time event. The risk of corrosion is always greater than zero and the risk could be as high as approximately 62% when there is no corrosion data for new formulas and derivatives of current formulas (line extensions). Figure 1 is a reproduction of the risk curve provided in the July 2016 Corrosion Corner. The graphs in Figure 1 illustrate that the risk of corrosion is significant when there is no corrosion data on a new formula or a derivative formula. Risk decreases as the corrosion test length increases (i.e., the amount of data collected) and risk decreases more rapidly with electrochemical corrosion tests to a lower magnitude than the risk for a corresponding storage test. Why is corrosion risk always a concern? Very small changes in formula chemistry can cause very large changes in corrosion behavior. For example, the number of SKUs Figure 1: The estimated risk of pitting corrosion as a function of test length. 32 Spray December 2016
Spray Decemberr 2016
To see the actual publication please follow the link above