WorldRadio September 2006 | Wires and Pliers

Homebrew Rust Remover

During a recent discussion on the MorseCode mailing list about rust removers, several commercial products were mentioned. One was Evapo-Rust, which, according to the manufacturer, was safe to use, was fast, and could be disposed of right down the drain. I bought a gallon of it to try out on some rusty parts of a telegraph key I wanted to restore. The lowest price I could find at the time was $15.00 per gallon plus shipping.

I used about a quart of Evapo-Rust in the test and it worked very well. It removed the rust from the key’s steel arm in two days. I did several items with equal success.

I went back to the Evapo-Rust website to research the product a little further. The process this product uses to remove rust is called chelation. The chelation agent combines with the iron oxide and kind of holds it in suspension. The result is a de-rusted object.

While searching the web for more information about chelation, I came across a list of a few things that are chelators, one of which is molasses.

If molasses is mixed with water at a 9:1 ratio, that’s nine parts water to 1 part molasses, it’s supposed to remove rust. OK, this is interesting. If this were true then it would be much cheaper than the commercial product. I asked my wife if we had any molasses. She found a 12 oz. bottle of Brer Rabbit molasses that had never been opened. I found a glass gallon jug in which to mix the brew. Now, how do I get the molasses out of the bottle? A kitchen knife didn’t fit the opening and it sure isn’t going to pour out by itsself. Tried hot water; but couldn’t get it hot enough. Then I put the microwave to use. By zapping it for 15 seconds at a time and checking the bottle for heat, it got hot enough to eventually run out. Be careful here, it heats up from the inside first. Check for pour-ability as you heat it up.

The gallon jug is just right for the mix. The 12 ounces of molasses mixed with 108 ounces. of water is nearly a gallon, which is 128 oz. I just filled the jug with water and mixed the molasses up in it. I figured the 9:1 ratio doesn’t need to be that exact.

My first test was the steel arm of a J-37 telegraph key. The top of the arm was completely covered with rust. The bottom of the arm was less rusty. I removed the arm and suspended it into the molasses mix with a piece of mig welding wire. Mig wire is copper clad steel wire, and I just happened to have it around for another project I was working on, so I used it. More on the wire later.

Most of the information about molasses/chelator said it would take up to several weeks to de-rust stuff. Since it took two days to de-rust another arm using Evapo-Rust, I checked the current test in two days for a comparison. When I removed the arm after the two days and washed it in tap water, I was really surprised. The rust just washed away. It left a clean steel arm.

So, now my interest was really piqued. I found a steel hole saw that had been left outside for a year. It was pretty rusty, as you can see in the accompanying picture. I decided not to scrape off any loose scale. I wanted to see how effective the molasses would be with the crusty rust.

I checked the progress every day for four days, and then checked it three times during the following four days. It was quite surprising how well it worked on the crusty rust.

Each time I checked it, I would wash it with tap water and dry it. Each time the rust would be thinner and more base metal would show through. When you look at the before and after pictures you will see a dramatic difference. I think the black spots are the remains of the original black coating on the saw blade. I looked at the surface with a 12-power jewelers eye loop, and there are some very small remnants of rust remaining.

It looks to me that the molasses chelation process is a keeper. It remains to be seen how long this batch can be used. At some point the chelation molecules will hold all they can hold and it will stop working. But, it’s hard to beat for the price. The local groceries had molasses for around $2.00 per bottle. $2.00 per gallon is much better than $15.00 per gallon plus shipping.

I mentioned the mig wire has a copper cladding on the steel. When I took the saw blade out of the solution, the copper had been stripped off the steel wire. So, there are probably some acids in the molasses that like copper or brass. I also tried an old brass key base in the molasses for about 12 hours. The bare brass had a copper color, which means the zinc has been removed from the brass. Test a throw-away piece before you try to de-rust a good piece just to make sure it won’t ruin something. More testing is needed on other metals to see how they react to the molasses.

To sum it up, molasses is a cheap way to de-rust steel. It’s a little slower than commercial de-rusters. I believe if I had scraped off the loose scale and rust, the process would have been faster. I later found out there are several types of molasses. The type I used is now unknown. I do not think it was a “lite” style molasses and I don’t recall seeing “blackstrap” on the label before I threw it out. The commercial chelation de-rusters target only steel oxides, so they will not bother copper and brass. Molasses may attack other metals, so take care how you use it.

Have fun de-rusting. Don Kemp, NN8B.