Without barrier protection in place, paper fiber corrugated cartons may cause corrosion on products stored within. In fact, even a product stored for just four weeks in a corrugated box that meets the archival standards established by the U.S. National Archives and is at the upper limits of the sulfur level specified, would see corrosive sulfur potential exposure equivalent of greater than 20 years of natural exposure. Four weeks is not a lot of time for shipping and storage, especially if that carton is shipped overseas and/or into humid, harsh environments where air pollution is prevalent.
Let us explain further. The US National Archives sulfur requirement for paper corrugate is less than .0008%, or 8 PPM, therefore the specification allows for a sulfur content of up to 7.9 PPM.
For reference, Intercept Technology packaging inventor Bell Lab’s Accelerated Atmospheric Corrosion Testing uses 4 PPM of sulfur to provide 10 years of equivalent exposure in three weeks. It has been proven that a concentration of 4 PPM of H2S has a linear acceleration factor in relationship to concentrations as low as 10 ppb. 4 PPM is an acceleration factor of 170 over natural levels of 35 ppb. If you were to calculate the sulfur level at the allowed limit of 7.9PPM, the acceleration factor would be 335 over a naturally occurring corrosive atmosphere. Given these facts, it is worth repeating: any item packaged for four weeks in a corrugated box that meets the National Archives upper limit, without barrier packaging, would be exposed to a potential corrosive sulfur equivalent of greater than 20 years.
Testing on paper corrugated boxes as a potential corrosion agent is supported by Birmingham Assay Office in its “Tarnishing” report. Founded in 1773, the Birmingham Assay Office has been a center of expert opinion and independent assessment of jewelry and precious metals for nearly 250 years. Excerpts from their report state:
- "The tarnishing agent is most likely to be free sulphur or a volatile sulphur-liberating compound, which can still cause problems even if not in direct contact with the product.”
- "Recycled paper and cardboard may be helpful as they have lower sulphur content than virgin paper, as well as lower levels of other harmful tarnish-causing constituents.” Note: As long as there are not other contaminates in the recycled paper.
- "Some synthetic foam, besides sulphur, contains high levels of chlorides and fluorides – both of which will cause tarnishing of silver and other metals."
Intercept Technology barrier packaging products naturally react with and neutralize sulfur gases without contamination, as it will for many other gases that may cause corrosion, including chlorides, fluorides, and nitrogen dioxide. Intercept products are easy to put in place without the use of oils, waxes, volatiles, and other labor-intensive components, so Intercept is safe for handlers, the products inside, and the environment.