Umm… dive it?
Seriously, these are industrial-grade cylinders. It will outlive you, even with its flaws…
ETA: here’s a tank I bought. Cleaned off the corrosion. Hydroed it: passed just fine. Do not worry about such microscopic details…
tl;dr: look at the photos, particularly the tank bottom. Is this tank worth saving, and if so, how should I do it?
I had previously asked for some details about some tanks I bought (
Question - Older steel 72 Pitt Depth) At the time, it seemed like they might have been galvanized, so I decided to move forward with them. I had put a light in them and knew they were a bit rusty inside, but no pits: they looked to be in solid shape. At a glance, the outside seemed OK: beat up, but basically sound. So I bought bands and valves for them, as well as some phosphoric acid, and...
ETA2: Rereading this, I may have come off condescendingly. That was not my intention. You’ll notice that in that thread above I was the one asking if my tanks were too damaged to be used, and everybody told me everything was fine: clean them up and use them. Of course, those tanks were slightly more corroded than what you’re showing us…
So I get it: brand new tanks and you’re worried. The point is: scuba tanks can take an unbelievable amount of abuse, and hot dipped galvanized like yours even more so. They will be fine. And for the record, that is most likely not really rust of your tank. It very well may have been something that rubbed onto your tank and rusted on the surface. But either way, the tanks are fine.