Written on: September 2, 2014 by W. Stephen Tait
Hello, everyone. In late July, I received a newsletter from one of our affiliate chemical testing laboratories that discussed the Ban Poisonous Additives Act (H.R. 5033) introduced in early July in the U.S. House of Representatives. A companion bill was also introduced in the U.S. Senate.
This is not a new bill. Indeed, the Ban Poisonous Additives Act has been introduced before in 2011 and 2013. In fact, the controversy/discussion over bisphenol A (or BPA) in epoxy resin coatings is multiple decades old (bisphenol A-epoxy has been around since the 1930s).
The epoxy resin coatings used for food containers, spray packages and aerosol valves are manufactured by reacting BPA with epichlorohydrin. Thus, BPA is a major component of spray package and aerosol valve epoxy coatings.
As with all chemical reactions, there are small amounts of residual BPA in the epoxy coating. It has been shown in some instances that some food products leach a small amount of BPA out of the container coating.
The results from a number of toxicological studies using low concentrations have been inconclusive. However, the potential human health implications have caused more discussion and more toxicological studies—along with calls for legislation banning BPA. Indeed, the U.S. Food & Drug Administration (FDA) has banned the use of BPA-epoxy coatings in infant food packaging and there are already a few states that have banned BPA-epoxy coatings in all food containers.
Normally, I don’t discuss legislation because this topic is covered in another column in Spray, however, H.R. 5033 would have a significant impact on spray packaging corrosion if the bill is enacted into law.
There are approximately 100 times more food containers than spray containers manufactured each year. Thus, the bill—if passed—would also probably cause epoxy coatings in spray packages and aerosol valves to be either discontinued or substituted by a different type of coating for the current internal epoxy coatings in spray packaging and on aerosol valves.
Aerosol valves with epoxy coatings are used in both traditional aerosol containers and the laminated foil bags inserted into them. Hence, the impact on our industry would be extensive if H.R. 5033 is passed into law.
Several decades ago, a number of epoxy coatings were developed that did not use BPA as a major component (in response to the BPA controversy). Some of these alternate coatings were water suspensions of non-BPA epoxy resins.
Corrosion testing on these coatings found that corrosion protection efficiency by the non-BPA epoxy coatings was highly variable. It was discovered with the non-BPA epoxy water suspensions that the type of surfactant used and the surface preparation prior to coating had a significant effect on the ability of the non-BPA epoxy coatings to protect the substrate metal from corrosion. Thus, most of these alternate epoxy coatings were found to provide less corrosion protection than the traditional BPA-epoxy coating.
So what happens if H.R. 5033 becomes law and epoxy coatings with BPA are banned from food containers? The result would be a lot of spray package corrosion testing to qualify new types of coatings for traditional aerosol containers, as well as valves on the laminated packages inserted in aerosol containers and aerosol valves that use epoxy coatings for corrosion protection.
Corrosion evaluation could be either electrochemical corrosion testing or long term storage stability testing. Electrochemical tests can be completed in less than 90 days with a high level of confidence when the appropriate test parameters are used to gather the data. Storage tests should be conducted for at least one year before making a decision on the commercial suitability of an alternate coating.
Please send your questions/comments/suggestions to rustdr@pairodocspro.com. Back issues of Corrosion Corner are available on CD from SPRAY. Thanks for your interest and I’ll see you in October.
