Brick acid

[Munkul]

Still available from farm supply stores as chlorinated cleaner for dairy industry.

Something like duosan red label would be a suggestion.

For example

Deosan Hypochlorite Red Label

All purpose hypochlorite disinfectant for general farm use.

www.moleavon.co.uk

One thing I would absolutely not recommend is mixing deosan hypo with any kind of acid.... gives a strong reaction and produces instant chlorine gas!
1st hand experience...

 

[brightspark]

i once sprayed a motorbike frame with the original hamerite in the shed over a gas ring used carbon tetra chloride thinners its fire proof yea the fumes off it nearly made me pass out and crawled out of shed apparently it gives of chlorine gas nearly learnt the hard way