[Fred Hayek]

If it is concentrated (>96%, maybe more) sulfuric acid, carbon steel works just fine. It's the lower concentrations, when it is ionized, when you have problems. Typically for a concentrated sulfuric acid tank the material would be carbon steel. If it is less than concentrated there would likely be a heavy epoxy coating in the tank. In the Houston Ship Channel area a likely use for H2SO4 would be in alkylation units in refineries.

[spunkets]

Yes a compact protective salt film forms on carbon steel in con sulphuric acid. As long as there's no water, the film doesn't dissolve. There is a corrosion rate of ~20 mils/year though. I was just assuming a 308 stainless would be cheap enough to relieve headaches.

They probably have some sea water in there. I'd hate to be nearby if that thing dumps. There will be quite a boil over. A long time ago I worked for a company with a division that had a 2500gal carbon steel tank holding con sulfuric inside the plant and in a hallway with offices along it. Idiots ran it. It ruptured, because of poor maintainance and contamination...pits and tunnels along welded seams. ~ 1000 gals of con acid ran across the floor, into all the sales and accounting offices in addition to the plant area. no one was killed, or seriously injured. They repaired it and within one year they did it again. Needless to say, except for the idiots, they had a high turnover rate and of course product rarely went out the door.