Molasses rust removal

W

wrndln

Well-known member
I have a rusted engine block I want to derust with molasses. I have a 100 gallon plastic stock tank I plan to use to do it. I bought some dry molasses at a local feed store to use. I don't know what the ratio of dry molasses to water should be for the best results. I have heard anywhere from 9:1 (internet search) to 3:1 (Fordbarn, I think), but I think that was liquid molasses and not the dry type. If anyone has had experience with derusting with molasses and used dry molasses, would you please post the ratio (either lbs or quarts of molasses to water) you used to get good results.
Rusty Nelson
 
Bill,
I can't get the link to work in your response. Also, did it work well for you and how long did the process take to remove all the rust.
Thanks,
Rusty Nelson
 
I used dry molasses and as I recall I mixed one pail of feed to 5 pails of hot water. I put it in a dark blue container in the hot summer sun, and it took about 1 week. The parts came out great. Rinse in hot water and blow dry quickly to prevent flash rust.
 
Sorry about the bad link. Fixed now.

I'm the webmaster and all of that site is maintained on my home system and then "published" on the club website. It's quicker to look at a page locally since I don't need to get it via the 'net. That's what I was doing and grabbed the local link.

As I noted in the write-up in the newsletter, I threw the parts in and forgot them, they were in for a week or so. I have been told that heat and circulation speeds things up markedly, but I cannot vouch for that.
 
I recently derusted an old Desoto engine block in a 55 gallon drum. I mixed about 8 parts dry molasses to water. Left in in about 2 weeks. I wish I had left it in for a month because parts I left in for 4 weeks came out cleaner than the block. Sometimes it helps to remove the part after a while and clean it off good and put it back in to
"cook" a little more.
 
Bill and 34 pickup,
When you give the mixing ratio, do you mean for example 8 gallons of water to 1 gallon of dry molasses? It looks like Tom mixes it a little stronger a 5:1. I want the "soak" to work well, but not waste molasses.
Rusty Nelson
 
Just guessing: when I mixed up my first 5-gallons, I think I may have used a quart or so of dry molasses.

Just mix some up. If it seems a bit slow acting, add some more until it feels about right. :-)
 
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I suggest greasing the machine surfaces if you don't want this to happen.
 
Russ/40,
Do you think the molasses caused the pitting or the pitting was already in the block before you soaked it? It is hard for me to believe that molasses could cause pitting in a smooth surface.
Rusty Nelson
 
It won't strip paint or grease, and also has ne effect on spark plug lettering. It does a good job on the rust though. I'm not sure what effect it has on aluminum or babbit.
 
wrndln said:
Russ/40,
Do you think the molasses caused the pitting or the pitting was already in the block before you soaked it? It is hard for me to believe that molasses could cause pitting in a smooth surface.
Rusty Nelson
Click to expand...

The molasses only attacks the rust not the metal. Those pits were caused by rust and the molasses cleans right down to the bottom of the pits.
 
You do have to watch the machined surfaces. I also had a cylinder head come out with those pits. The machined surface did not appear to have a lot of rust on them before hand so I am not sure what happened. I did have the heads in the stew for several months though.
Rusty, I had read that 8:1 was a good ratio so I would put about 8 gallons of water in a drum and then a gallon pail of dry molassas, mix it up and continue until my 55 gallon drum was full.
 
Those of you in denial that the Mollasses did this, be forewarned. What does not show in this photo is the bores were just as bad. This engine had a fresh build with a bore job and new everything, that I picked up real cheap. The water jackets were pretty rusty, so I thought I could clean those up with the Mollasses soak. I used a 5/1 mix for 5 weeks. Every machined surface was pitted, including the intake valve seats. It was a 51 block so it only had hard seats in the exhausts. Painted and greasy surfaces are not affected by the Mollasses. This was not the result of pre existing rust. It became one very expensive motor, as it had to be decked and bored with new pistons as a result.
I suggest if you are determined to do this, you remove the block every week and clean a machined surface inspecting it very closely. There is a slime that builds during the soak process that hides the pitting if you don't look closely.
 
The molasses DID NOT DO That the stuff IN FEED molasses did it . I got on here several years ago and got called everything in the book.
All you have to do is look at the INGREDIENTS in FEED molasses, the protein % in animal feed is the amount of UREA that is added + a hand full of others. Urea is made with ammonia for one and used in animal feed fertilizer and IS NOT metal friendly for sure. I have tried to see how it worked it will mess up good metal smell so bad can't get close to it after a few days.

I use molasses from the mill and use it one to three or four works good that away one gallon makes five gallon mix. I keep mine about ten feet from my drive and almost never smell it and then only molasses smell. I have put every thing I can think of in it and left them for weeks and weeks even a year on things I did not need and never had anything pitted. Brass, Copper even bearings all come out looking good. I buy molasses from the syrup mill 55 gallon drum 60 cents.
Maybe you can find a feed mill that gets molasses by the tanker and get some before the mix it.

I have a few pictures but don't know how to put them on B.flournoy@att.net
 
Just have the block cleaned the professional way, shake and bake and get a better result without risk and the hassle. That's my two cents. Every time this topic comes up I make the caution, but people don't listen. Yes, I used feed molasses, after being told plain molasses won't do anything. This is my last time addressing this issue.
 
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