Just in case it is interesting to anyone, here the manufactures report that was in the DiveRite/Halcyon OPV spring recall report (NOT ANYTHING TO DO WITH EDGE PRODUCTS). I have no clue how to read it. Nor do I know if it is what their bad springs were or what the good ones were supposed to be. I would be curious to know if anyone understands this and has any comments about what it means.
http://sumnermckenzie.com/DiveRiteOPVspringSpecs.pdf
Although the analysis, doesn't specify iron content, adding up what is there says this is 304. My experience with 304 is that it WILL corrode in SALT water IF it is not rinsed off with with fresh water. Springs are thin and any corrosion could weaken them. So if you put your BC up for the winter without rinsing the dump valves throughly of salt, this could start a corrosion process. Remember the salt can crystalized on the springs if not rinsed off before it is allowed to dry on its own, this could lead to a build up of salt crystals on the springs. This would require a thorough washing of the valve with fresh to dissolve the crystals.
316 stainless has superior corrosion resistance to 304 stainless in salt water. Fresh water doesn't attack 304. 316 doesn't care if its rinsed or not and it will look new even in heavy brine even after years of contact exposure. Springs are available in 316 SS
However, 304 is superior to the 400 series of SS, which will readily rust in saltwater but 4xx will not rust as quickly as regular steel. I can't tell from the report if these are the new springs or not, maybe the previous springs were of the 400 series making them deteriorate more quickly.
It doesn't take much time to weaken a 20 guage spring when put in a corrosive environment and the dump valve spring is more or less hidden from view so it takes more care to rinse it properly if it is not 316 SS.
Why not always use 316? Because 316 is more expensive than 304, and other SS, not alot more in cost but certainly more, and then you have people in the chain of manufacturing that could care less what the spring is made of knowingly or unknowingly substituting the part of a lessor quality for the job. It takes a keen eye to spot ("suspect") the difference between 304 and 316.
It should be the responcibility of the valve manufacturer's QA/QC department to ensure that all parts remain as specified by the engineers with random tests performed on each batch of parts (springs) received from a supplier. This is not likely done unless they happen to have their own SA machine. Otherwise they would have to forecast their parts usage to include time to get results back from a lab before a batch (of springs) could be placed into parts bins for immediate manufacturing use.