Molasses has been around for years and has to be one of the best value ways of removing rust on STEEL panels (alloy and molasses can equal one rooted item).
My brother in law is very big into old cars and has been for years and had a HUGE tub down the back that could take panels, cowls, doors beams etc etc and most times it only took a week of being in the bath to get rid of all rust safely. I've done the same thing on a much smaller scale with heaps of success and when the molasses solution is fresh it's safe to handle (not sure after umpteen uses as I never kept it for long as it's cheap and easily renewable)
A strange spin off is the parts I've done haven't suffered any further corrosion even in a damp environment - something to do with the chemical reaction that stabilises the surface.
If it is deep rust it might take a few immersions with scrubbing and hosing between baths but it will eventually remove even deep crusty rust.
I used it at 4 or 5 to one but have seen it thinned almost double that mixing ratio.
When you are done you can tip it down the dunny or into the garden so long as there isn't 300L of the stuff.
Dave Mac
I'm not sure if molasses is 'self limiting' to just the rust - it might start eating good steel if left in the bath for too long.
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