apple pie construction showing stitch and glue method of boatbuilding

Using Molasses to remove rust

I had always wanted to test molasses as rust remover and while I was getting my clamps cleaned up and ready for a new boat build, I ran across a pile of rusty old clamps I had rescued curbside.

jug of molasses jig to make hidden joints

Ages ago I had picked up a gallon of feed molasses from a farm feed store, while I was getting some bird seed. It is very inexpensive. This store sold it to add to horse feed. Apparently the horses love it.

Instructions for dilution range from 10 to 1 to 4 to 1. I'm not sure it's all that critical. I'm closer to 10 to 1.


rusty clamps rusty pliers

I threw in the old clamps, a rusty pair of pliers and various bits of rusty iron.

If using molasses to clean rust works it would be a very simple, safe and cheap method.


rusty clamp

I'm not sure what this clamp is used for, I'm thinking maybe to hold a pipe. There are 2 spots that have screws.

Note: I've since found out that similar clamps are used in setting up lights in the entertainment field, among other uses.


after 1 day

I peeked after one day and was surprised to see the molasses solution had already removed some rust from a base plate and from the pliers. One corner had been sticking out so it shows how much rust has been removed.

The general feeling is that it takes a couple of weeks to a month to remove rust using molasses so I was surprised it had worked so well.


Why does Molasses remove rust from iron?

Apparently molasses contains chelating agents. In practice the chelating agent binds with the rust and makes it water soluble. The rust dissolves into the molasses solution and clean metal is left behind.

Chelating agents are talked about in 2 main applications. If there is a case of heavy metal poisoning then a chelating agent is administered and this makes the poison water soluble and releases the lead, mercury etc. and makes it possible for the body to excrete it. In agriculture, chelating agents bind with minerals and make them more readily available to plants.

I tend to blank out a bit when it comes to chemistry. This article is at least readable. from the University of Wisconsin-Madison. It defines a chelate as: ..." a chemical compound composed of a metal ion and a chelating agent. A chelating agent is a substance whose molecules can form several bonds to a single metal ion."

Apparently the chelating agents found in molasses, mainly cyclic hydroxamic acids, are responsible for molasses rust removing talents.

These cyclic hydroxamic acids are particularly effective to chelate iron and make it soluble.

It seems that molasses works for iron but can damage other metals so use it only for iron rust, not all corrosion.


How well did molasses remove rust from iron?

It's been exactly 7 days since I've thrown the clamps in the molasses solution and 5 for the plyers and a couple of other things.


mold scrubbing

The molasses had started to ferment some and there were a couple of spots of mold.

I fished out the metal from the molasses bucket and put them in clean warm water to rinse and warm up. My shop was cold and the molasses was freezing to touch.

I scrubbed the pieces with a 3 m scrubbing pad and a brass wire brush. If it was good enough I put it in another bucket. If it was still too corroded I threw it back into the molasses.


clean clamp plyers

Some pieces were very clean. All the orange crusty rust was gone. The molasses did not seen to change the black "rust" and I don't mind.

The plyers were much improved but after scrubbing them, I threw them back into the molasses.


oiled clamp

It was very interesting to see that if any of the cleaned pieces actually dried without oiling they rusted immediately. I kept all the scrubbed pieces in a clean bucket of water till I could dry them and immediately oil them.

Here are the clamps and other metal that I cleaned and oiled. They are greatly improved after only one week. The rust is gone and the exposed metal is gray but smooth. The screws run smoothly in the clamps. This is a great success. The large clamps and pliers will stay in the molasses for another week.

Meanwhile I can see running a bucket of molasses to remove rust from tools, every few month. I have loads of junky tools I've picked up here and there and this might work very well to restore some of them to life and use. I picked up a bunch of rusty files from the curb a few years ago (yes I'm a pack rat) and I'll try these next.


clean clams

Here is the final result. After 2 weeks I fished the remaining parts out of the somewhat fermenting molasses, remember there are no nasty chemicals to kill stuff. I scrubbed with a wire brush and dried and oiled the lot. Not bad if you compare with the first photos.



I try to be accurate and check my information, but mistakes happen.

email me if you find mistakes, I'll fix them and we'll all benefit: Christine