cheap rust converter

hey,as you prolly all know the active ingredient in rust converters is phosphoric acid. i've just found out that milk stone remover,available from farmers suppliers,contains 35% phos.and this is the best bit it only costs about a tenner for 5 ltrs.i reckon that's enough to keep feo2 at bay for a while.

Acid-Brite (from a company in preston) for dairy plants is 60% phosphoric acid and can be sprayed on with a garden pressure spray for bigger areas, and doesn't damage paintwork......so I am told.