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Spray January 2017

W. Stephen Tait, Ph.D. Chief Science Officer & Principal Consultant, Pair O Docs Professionals, LLC Corrosion Corner Spray Package Corrosion Risk—Part I. correlations between electrochemical corrosion test predictions and their corresponding actual commercial spray package corrosion. The data used to generate Figure 1 were obtained from corrosion tests on a wide range of household spray products, personal care spray products, health care spray products and commercial spray products. The curves and correlations in Figure 1 are aggregates for all data and are not for individual families of products or specific spray package-formula systems. The Y-axis for Figure 1 is the localized corrosion probability for spray packages and the X-axis is the length of a corrosion test in days. In other words, the curve provides the probability (risk) of localized corrosion in spray packaging as a function of test length. Localized corrosion was chosen as the metric for Figure 1 because it leads to package metal perforations with subsequent product and/or propellant leaking and delamination, such as blistering that could potentially produce loose pieces of coating or laminate that clog valve orifices. The storage test curve in Figure 1 is for traditional metal aerosol containers. Risks for multiple times were generated because a traditional storage test typically takes one year to complete in order to obtain a risk below 10%. Figure 1 depicts the probability of metal pitting corrosion. The data for Figure 1 were obtained from: • uncoated tinplated steel aerosol containers (ETP) • all types of epoxy coatings on ETP aerosol containers • epoxy, Polyamide-imide (PAM) and coated aluminum aerosol containers • all types of epoxy coatings on tin- free-steel (TFS) aerosol containers We do not have enough data for generating similar curves from storage tests on TFS containers with other types of coatings, such as polyethylene terephthalate (PET) and Happy new year, everyone. The May 2016 through August 2016 Corrosion Corners have a series of discussions on corrosion risks with spray packaging, how the cost for corrosion failures is significantly higher than corrosion testing, as well as the difference between risk management and gambling and how corrosion prevention and control is a continuous process and not a one-time event. All these discussions centered on a figure for the risk of spray package corrosion as a function of test time for the traditional storage corrosion test and electrochemical corrosion tests. I received many requests for a more detailed discussion on this figure and decided to start the detailed discussion this month. The discussion is long, so I divided it into two parts—Part I is this month and Part II will be in the February edition of Corrosion Corner. Figure 1 contains the risk versus time curve for storage corrosion testing with traditional metal aerosol containers and Figure 1: The estimated risk of localized corrosion as a function of test length. 24 Spray January 2017


Spray January 2017
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