Ed Hatfield:
The answer partially depends on the conditions of filling that led to rust formation. If you have been regularly getting moist air boat fills over several years, you may have a problem. But, if you have a bit of flash rust, that is usually not an issue. I dive double PST HP120s, and tumble them when I O2 clean them each year. Last year, there was no rust visible in either tank at the time of VIP, year before that, there was very light flash rust visible in one tank, nothing in the other (even though they are manifolded and therefore get filled the same each time). As others suggest, have them tumbled, then take a look inside and you should be able to tell very easily if there is a problem before sending them for hydro.
