jimmyt: If winemakers have been using H2SO4 (sulphuric acid) to rinse their barrels, I'd certainly avoid the stuff!
H2SO3 (sulphurous acid) has been used for centuries to sterilise barrels and stop wild yeasts spoiling the fermentation. Traditionally burning a bit of sulphur paper in the empty barrel which was rinsed afterwards (They were certainly still doing it this way in the 1960s when I worked one summer in a wine cellar in Mainz).
Adding sulphite to the wine is something else.

nick