I bought 20Litres of molasses for maybe $5 ?( or was it $two) from the local sugar mill late '90's, works a treat, I have bucket up the back and just drop things in at random....needs changing now though....I still have about 15 litres of the 20.
The items need rinsing off after, but brings it up like sandblast, trouble is then the surface can start to rust again, but wire brushes off easy..I did my tank with it, but became labour intensive, and still needed to rinse it out with Phosphoric finally gave up and just put fuel in it...