De-rusting with molasses

Terry NJ

Terry NJ

Well-known member
A while ago, I recall Tom W. referring to rust removal with molasses. If Tom reads this, could you please go over it again. How much? what to mix etc?
Yesterday, I bought a chrome stone guard but it needs cleaning and I remembered that thread.
Terry
 
There are some good videos on YouTube regarding the use of Molasses as a rust removal agent and some include an Aussie doing a whole car. Me, I used it for years in doing my old coupe and many other car parts, even brake assemblies for my Model A.

I use dry molasses which is easily obtainable from a farm or garden supply and generally is inexpensive for a large 40 lb. bag. The amount or scoops I used were not critical in the least, but as best I recall, I used 2-3 scoops to a gallon of water. I used a clear plastic bin to keep the parts in and put it out into the hot Texas sun for a day or two. The residual sludge mix will begin to smell after a while and I would not pour it out onto any vegetable garden to dispose of it. Evan after rust is removed, you still must treat the part immediately or flash rusting will occur. Even if you can't readily see it, that rust begins immediately if the part is not cleansed and a primer or protectant isn't applied. The reason I used the clear plastic tub was of convenience only and the idea that I could see the parts without having to first remove them. I suppose if you didn't have a hot Texas sun any other would likely do though. :-)

Here are some photos, but Vinegar can also be used as a derusting agent and have good results, as well. On YouTube, look up n a search for electrolysis or electrolysis by molasses and you can probably fins more than you wish to know about the process.

Here are some very random photos. The fellow who did the old car (coupe) on YouTube had it all dunked. I have done larger parts by use of a plastic kiddie pool, but you have to be careful with any sharp edges that a fender or such my have and emptying it out afterwards can be messy as the pool becomes very heavy with the water and all.

Good luck on your project.

Here is a link to the video I mentioned:

https://youtu.be/KZCFcxf5IBw
 

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I seem to recall using about a gallon of dry molasses to 10 gallons of hot water, then put the dark colored tub in the hot summer sun. It took about 5 days and my parts came out rust free. It didn't remove any writing on the spark plugs and it doesn't remove grease not paint, but worked great for rust. As mentioned rinse in hot water and blow dry immediately. Paint as soon as possible.
 
I am not Tom, but I have used molasses to derust a stubborn clamping strip that holds the upper and lower back panels together on a 28/29 CCPU. The remains of one of the flanges was rust welded to the inside of the clamping strip. I tried Evaporust, ATF & acetone, and a couple other rust removers. None of these removed the hard black rust on the inside of the clamping strip. I finally bought some dried molasses at a feed store (it is usually used as a feed sweetener for animals) and mixed it with water. I used a pound or slightly more of dried molasses to a gallon of water. I let the clamping strip bathe in the solution for about 3 weeks in the top of my hot barn. I think the hotter the better for rust removal. After the long soak, the hard black rust turned into a thick paste. I could scrape it out of the clamping strip channel with a putty knife. It wasn't real easy, but in about 15 minutes I had all the crud and remains of the upper panel flange removed as well as the rust. The molasses and water kind of ferment and stink, so you don't want to have it setting anywhere you don't want a putrid odor. I am posting a picture of the Evaporust soak that didn't work, but the molasses soak was the same setup, except for the brown molasses instead of the Evaporust.
Rusty Nelson
 

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Avoid cast iron pieces that have machined surfaces. They will pit terribly wherever the machined surface is.
 
I have used molasses for years and it works really well, as long as you're not in a hurry. I buy it from dairy farmer friends at a ridiculously low cost of $NZ300/tonne. I have achieved excellent results mixing one part molasses to six parts water and leaving it submerged for ten days. I occasionally stir it up to prevent it settling out. I don't think the temperature is important as I have got the same results in cold frosty conditions. After ten days I use a water blaster to remove the molasses and black residue and then apply a primer as soon as possible. I often get a flash-bloom, but sometimes no rust forms for days afterwards. I am not sure why that is - maybe it depends on the grade of steel. Yes, the plastic tub stinks a bit after a few weeks.

So molasses is a winner for me and I am surprised more people don't use it. Its cheap, safe, non-toxic, environmentally-friendly and easy to dispose of. And unlike electrolysis it does not produce potentially explosive hydrogen gas.
 
Thanks Guys! this is what I'm looking for. But I have one more question, How does it work with plated surfaces? Will it affect the chrome plating?
Terry
 
My experience with an engine block is Don't! It's OK to put it in the water jackets, but if you submerge an engine block, long enough to do some good in the water jackets, it will pit the machined surfaces. The active ingredient in the mix is sulfuric acid.
 
For relatively small parts, I use muriatic acid a lot for removing rust.
It works well, and it works quickly, it's not expensive, and you can use it multiple times.
I buy the 2 1 gal. containers sold for use in pools for about $10.
For small parts that aren't super rusty, it'll clean them up in a matter of minutes.

You submerge them, and when you're done, rinse it off with water, and dry. You just have to pretty quickly paint it, or wipe it down with Gibbs because it will flash rust.

I also use this for removing the zinc coating from nuts and bolts if I need to weld them.

Just another option for you guys.
 
There is also a product using beets or beet juice to derust. I think it's called "RUSTBEETER", but am not sure on that. I've never tried it, but the guy selling it at Iola said it works faster than molasses.
 
I love diy ideas that somehow work for specific needs. When I cleaned up my old tudor frame, I wish I had thought of this mod back then to remove some of the heavier scale where electrolysis or some other method would not have been practical. Heck, I even had the air hammer and compressor back then. I have seen some old mud bog Jeeps which this may have done some good as a tool to use, too in prepping a frame. It isn't directly related to molasses rust removal, but is just a trick or mod which may come in handy when one does some rust removal on certain areas.


https://youtu.be/dCEdhlDteJo
 
I guess you shouldn't use it in January (slower than molasses in January)
I had a customer use it on an engine block and it did pit the machined surfaces real bad.
We had to remachine every thing.
 
Since the sludge or goo gets thick in a molasses container as parts lose their rust and all, I would think it a bit unwise to use it in an engine block where contaminants may end up getting lodged where you could not see to remove them. I never tried such, but that would be my logic to keep me from doing it to begin with. Even with any flushing, I am not so sure you gould get everywhere to remove those gummy parts or contaminants trapped inside the block.
 
Mad Mac said:
I don't think that is correct. Its not an acid - it works by a process called chelation (Google it) :)
Click to expand...

If you look at the ingredients it has sulfur in it. To me, that is a mild acid. I could be mistaken. I do know it ruined a V8 block I submerged in a 80 gal barrel for several weeks with the intention of cleaning the water jackets. I used a liquid mix I purchased at a feed supply. I checked it after two weeks, and it was covered with a sludge like deposit that needs to be scrubbed off. I didnt notice the pitting until it was too late. I would never do it again. JMHO
 
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