DRANO
CRYSTALS -- Sold in a CAN for about $3 at Lowes or Home Depot. Use it for stripping anodizing off fittings.... Mix up a batch in a plastic bucket - add water.... string the fitting on something (I use bent welding fill rods) and dip them and strip them.
It takes a FEW SECONDS..... if you have the mix 'right' -- if it doesn't start boiling -- add more crystals....
Warning -- do not breathe the fumes! LOL -- ask me how I know...