getting rid of rust

[clee]

G'day all, i was wondering if anyone has used molasses and water mix to get rid of rust. I read about it years ago but don't remember the mix. At the moment i am trying a 50- 50 mix to see how it goes. Any info?      Regards Colin Lee

[Dave]

Hi Colin,

I haven't heard of the molasses treatment before. What part is the rust on? And is it surface rust, or more heavily pitted into the metal?

Dave

[clee]

G'day Dave,  the rust on the parts i am doing at the moment are only light rust, but if it works ok i will put some rougher parts in.   regards Col.

[Dave]

A search on "molasses" and "rust" turned up some interesting articles. This one from the Morris Owners Register in Victoria is a pretty good summary.

Everyone has heard how molasses dissolves rust, so make a trip to the local pet food and grain store and get your molasses.
The formula is two litres of molasses in 7 litres of water. Put this mixture in a plastic bucket or container and partly cover to help stop evaporation. Leave for about three weeks, down by the back fence (it pongs a bit), until it ferments. It should now have a skin on the top, which should be peeled off. Now you can immerse your rusty parts in this solution. Leave for about two weeks before removing them, by then all the rust should be dissolved (use rubber gloves, long tongs, or tie pieces of wire to the parts before you start, as this mixture contains ACETIC ACID).

After removal, wash off the brown muck straight away with a stiff brush under hot running water. As soon as the parts are dry, treat them with rust converter and paint them as soon as possible, or if not painted, wire brush and oil them. This must be done immediately because surface rust will start to form as soon as the metal is dry, because it is so clean it has no protection.

Apparently the water and molasses mixture when left exposed to air, ferments and produces, amongst other things, Acetic Acid. This reacts with the oxygen in the rust and when the iron oxide (rust) is all reduced the process stops, so the steel or iron is not affected, but the surface of the metal is now virtually in original condition and subject to immediate attack by oxygen in the air and begins to rust, so must be protected.

The benefit of using molasses is that it dissolves that rock-hard rust that even wire brushes can't touch and carborundum cloth can't reach and by using arrangements of odd-shaped containers like old concrete troughs half full of dirt and lined with heavy plastic sheet, it is possible to derust larger objects that would not stand sand blasting.

This mixture will still derust for quite some time, (six months or even more).

Source: Morris Register of Victoria - http://www.moreg.org.au/dissolving_rust.htm



Another page has a first hand description of using molasses on some Jaguar parts plus some before and after photos -  http://inetogether.net/jaguar/

Here's a guy who does it in a swimming pool (!) - http://www.stovebolt.com/techtips/rust/rust_molasses.htm

And for a more chemical explanation, about a third of the way down the page - "Why Molasses Gets Rid of Rust" - http://www.lametalsmiths.org/news/page9.htm

Molasses contains chelating agents. These are made of molecules that are shaped a bit like the claws of a crab--the word chelating comes directly from the Latin word chele, meaning claw. They can envelop metal atoms on the surface of an object, trapping them and removing them. Molasses owes its properties to cyclic hydroxamic 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 microorganisms 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.   ... continued

Source:   Louisiana   Metalsmiths' Assoc. - http://www.lametalsmiths.org/news/page9.htm

Based on all this, it looks like it's worth trying. You might need to alter your solution ratio though Colin. 50-50 sounds a bit strong compared to what these people have been using.

Dave

[clee]

Thank's Dave, i will adjust my mix and see how it goes. Just as a matter of interest, one piece of very lightly rusted steel i put in the 50-50 mix is almost clean after 24 hours of imersion. This might save all of us a lot of work by the look of it. My shed is a bit smelly today but i figure it will be worth it. If you like the smell of rum it won't bother you too much.   Cheers Mate      Regards Col

[graeme]

A word of warning about the molasses treatment - make sure no alumimium goes into it. I know of someone who tried to cean up a gas headlight using molasses and all the aluminium rivets, plus the reflector dissolved away! Made for a lot more effort in restoring the light I can tell you!

[clee]

Thanks Graeme,  that is well worth knowing.   Regards Col

[Daren W Australia]

Hi I was told it damages cast iron as well Regards Daren

[clee]

Thanks Darren,  I will try test peices before i put anything in that is not easily replaceable.  regards Col