Why are molasses used to clean rusty surfaces?

Molasses contain chelating agents. These are made of molecules that are shaped a bit like the claws of a crab — the word chelation comes directly from the Latin word cheley — meaning claw.

They can envelop metal atoms on the surface of an object, trapping them and removing them.

Molasses owe their properties to cyclic hydroxmic acids which are powerful chelators of iron.

More of these compounds are found if the molasses is derived from sugar beet rather than cane sugar.

The plants from which molasses is made presumably use these chelating agents to help them extract minerals from the soil. Interestingly, there are aerobic micro organisms that use similar cyclic hydroxamic acids to scavenge iron. So plants and microbes appear to use the same chelation strategy to obtain their daily ration of iron.

The same process is at work when you clean old coins with Vegemite or cola. The power of chelating agents also explains why the insides of tomato tins need to be lacquered.

The citric acid in the tomatoes would dissolve the metal of the container if the lacquer were not present. Household cleaning agents, especially detergents and shampoos, also rely on chelation.

These soften water to make it more effective during the cleaning process. Chelation has its uses in medicine, too.

EDTA or ethylenediamine tetraacetic acid is used as a chelating agent to control levels of calcium in the body and can reduce the effects of mercury or lead poisoning. 

Source : The Hindu