Why O-Rings In The First Place?
Rod cases, especially aluminum cases use o-rings to prevent the aluminum parts from seizing together as aluminum will do and also helps keep the case cap snug against the threaded collar and not so much to prevent moisture from getting into your rod case.
Rod case o-rings are subject to cracking and breaking over the years, especially being exposed to sunlight, although the main reason for cracking or breaking is the exposure to ozone. This is called ozonolysis and this mainly occurs in nitrile rubber O-rings, including Buna and Buna-N varieties which are the O-Rings that we use for our rod tubes. Nitrile rubber is a polymer made up of units of carbon, hydrogen and nitrogen. The makeup of the nitrile molecules is such that there is an inherent ‘weak spot’ within the molecule. This spot can be susceptible to an oxygen atom being ‘donated’ from ozone, which breaks the chain and weakens the material. Over time, these tiny cracks caused by ozonolysis get larger and more serious, until eventually they are large enough to be seen with the naked eye and may eventually break.
So how do we prevent the ozonolysis process? Simply try to keep your rod cases out of the sunlight and even fluorescent lighting too as much as possible. But over time you may still have o-rings go bad and you need to replace them. Custom Fly Rod Crafters have Replacement O-Rings for both the 1-5/8″D and the 2″D rod tubes.