Thread: Anyone used molasses to derust??

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We were talking about dipping the new 455 block we got for Dans car in a solution of molasses and water for about a week to clean out the water passages and some of the surface rust that has formed from sitting. We figured this would be a good start for the hot tanking the machine shop would do.

I've done some research on the internet and some people swear by it but Dan says he found some info that it is hard on machined surfaces. The forums I looked at didn't mention that at all. So, have any of you used it for engine blocks or other parts that have machined surfaces? How did it work overall?

Don

i have a hot tank with zep vat stripper in it .the zep will eat rust very bad stuff . then after that if need to be cleaned abit better then a cup wheel on a angle grinder first wet the block with Wd 40 to hold down dust .i have vap a rust in 5 gallon jug i have used .one thing about any of this stuff is when it eats the rust out you end up with pits LoW spoTs the bores and deck on rebuilds get bored and the deck gets put were it needs to by crank shaft and cam center line ..blue printed .then i base my boring bar off the new true deck . so bores or deck will clean up less very bad pitts in the bores were i have had to sleeve more then one block from bad pits in the bore. there many photos of some of the steps in my photos on here just never posted many how i do things post on here . some shops just have jet washers only they do not eat much off blocks but if you work with all new stuff them its mostly oil and grit .some shops have a bake and blast setups were they heat and then shoot the block or parts with chopped steel wire or small beads if any of this stuff fall s out on a rebuild bad thing s can happen , hot tanks.. the parts soak in the tank so many spot get clean were other way may not get it clean. bad part is getting the bad stuff hauled away $$$$.i spend more money and time in cleaning parts were you do not really recoup this in the engine building part of the game but every thing must be clean to start any work . i use hot tank .jet washer. parts washers . bead blaster . then ebow grease. not in this order but this is the stuff i may used to get things clean older or oem engines are rusty and dirty i know some machine shops send out there nasty stuff to get cleaned so you may want to ask them how they clean there stuff they may have a hot tank or bake and blast setup so you not wasting you time as your only going to get it so good and then they may want to hot tank it any way .you may want to prep the block for them smooth the casting lines/core sand .flash. stuff hanging in side and out and ruff stuff if there going to put the cam bearings in so your not grinding /sanding on the block . then your just doing the final wash when there done

Don't know about de-rusting, but some Blackstrap Molasses added to a pot of navy beans on the stove will help quite a bit, along with a ham hock.

Originally Posted by techinspector1

Don't know about de-rusting, but some Blackstrap Molasses added to a pot of navy beans on the stove will help quite a bit, along with a ham hock.

abit of brown sugar...

I was wondering who the first one would be to come up with some molasses joke, and here it had to be you, Richard !

Pat, it seems most machine shops have been banned by the EPA or whomever from using the strong stuff they used to use years ago to hot tank motors. The ones I have gotten back in recent years show a little rust inside the cooling passages, and that is what we are trying to get rid of before the machine shop gets it.

Supposedly, the molasses you need to buy are the ones you get from feed and grain stores and it comes by the 5 pound buckets or so. It is used in animal food for livestock, I think. When it ferments it turns into something like Ospho and attacks the rust. It is a slow process and if you heat the mixture it works faster, so in Florida we should be able to put it out in the sun and let it do it's thing.

What about plugging the water ports and dumping swimming pool acid in there? I have heard that will clean out the rust.

Don

there no band in my state and i am registed with the DEQ and zeps sell s me the vat stripper its mostly the cost of having the hot tank .its not for the back yard engine rebuildes

A friend of mine has been using molasses for some time now,,in fact he has a 351w in the tank,or had it in the tank..He has soaked numerous blocks,and swears by it..Hope its good,cos that 351 will be built up for our F100.

Has you buddy ever said anything about machined surfaces being attacked? I can't see how those would be any different from regular bare steel, but Dan says some Model A forum thread said it is a problem.

Don

Don,
I've looked at this before, saved a link or two, but cannot give you any personal experience as I've never tried it yet. If you Google 'molasses rust removal' you will find tons of threads discussing the process. Here's one I saved that talks about three or four different methods, including electrolysis using a battery charger which is a bit unique. I had a tip a while back about rust removal I believe that the "attack on machined surfaces" is simply the removal of rust on those surfaces, leaving pitting behind as Pat described, and I would think that any method used is going to result in the same surface roughness - machined surfaces rust, and when the rust is removed the formerly smooth surface is now rough.

i know a guy whats used molasses its about the same as the stuff i use called evap a rust . it just a verry mild acid from mother nature and is not toxic .if pitts are under the rust there going to be pits . any mild acid will work SODA POP . i would watch any acid hotter then this stuff were etching could occur

Originally Posted by pat mccarthy

i know a guy whats used molasses its about the same as the stuff i use called evap a rust . it just a verry mild acid from mother nature and is not toxic .if pitts are under the rust there going to be pits . any mild acid will work SODA POP . i would watch any acid hotter then this stuff were etching could occur

Very good info . I was also going to suggest soda pop. I also remember reading that you could dissolve rust in a tank of water with a battery charger and electrodes inserted into the water. Something like this, be careful with this. I also dont know if the process will give some kind of weird charge to the block that could interfere with electronics later on. just a idea.
YouTube - ‪Geoff's Science Garage - Electrolytic Rust Removal‬‏


Another idea is naval jelly and wrap the block in a trash bag for a bit.
But like Pat said , if theres rust there is pits. After the rust removal you will still have the pits.

The acid being discussed here in soda pop is phosphoric acid, one of the ingredients of Coca Cola.

I remember when I was a kid and riding with my dad at night when it was raining, the cars in front would throw up a spray of oily water onto our windshield and the wipers would smear it so that you eventually couldn't see where you were going. He would stop at a market and buy a bottle of Coke and pour it onto the windshield. The phosphoric acid would cut the oil off the glass and we could see again. In that era, most cars leaked or burned oil like crazy, not like today. There was a strip in the middle of every roadway about a foot wide that was solid oil and grease and black as coal. I'm just bringing the youngsters up to speed here, because they will likely never see that.

The water is pretty hard here in Arizona. Mineral deposits settle out in the bottom of the toilet and form a layer of buildup that just about has to be chiseled out. The easiest way to remove it is to pour in some swimming pool acid and let it sit for 5 minutes, then flush the toilet. Presto, squeaky clean.

I've not used the molasses thing, but have used phosphoric acid, vinegar, and oxalic acid for rust treatment. I'd recommend agains pool acid (known as Muratic Acid, which is hydrochloric acid...HCL) it's much more reactive and thus requires considerably more care, and harder to neutralize and dispose of. I'd typed out a long discussion of the one's I used earlier today, but the site had a hiccup this morning and ate it.

Oxalic acid is the primarly ingreadiant in CLR, a product marketed for household use to remove rust and mineral scale. As a practical matter that may be the easiest/best/safest product for a one time/hobby project like a block. If you've got facility or vendor support, the more aggressive acids might be viable.

Products like Ospho, naval jelly, Rust Mort, and most other commercially available brand name rust "converter" products are phosphoric acid based materials, so if you buy straight phosphoric acid you can avoid paying for dyes, advertising, packaging, and all the rest of the convenience costs.

I hate to confuse it more but I remember reading some where that the acid used could also change the molecular structure of the surface on the metal its placed on. I dont know how this would affect your application, if at all? Soda Pop should be watered down so that its effects will be slower,weaker, that straight phosphoric acid.
Another idea to remove the rust could be to get a couple kids and give them some wire brushes/

Oh ya, I have not used molasses.

No wonder I get an upset stomach from Coke ! I remember hearing years ago you could use it to clean rust off of bumpers, too.

I agree with the damage to machined surfaces not being caused by the molasses, but by the rust that was there already pitting the metal, and then once the rust was gone the pitting was evident.

I borrowed a product from my Son Don one time, called Evaporust, that he bought at Northern Tool. He used it and didn't like it, but I soaked some cowl lights in it that were really rusty and after an overnight soak they literally came out like brand new. It made the metal look like the day it was made and it left the painted parts intact. I think we might fill the cooling passages with that product and leave it overnight or so and see how that does. When Don used it I think he did a quick soak, so the secret seems to be overnight or more.

Today I called some feed stores in the area and found out what you need to buy is "liquid molasses". Two local stores sell it, but one wants to sell it in no less than 100 gallon quantities........they want $ 1.25 a gallon. The other store will sell it in quantities of 5 gallons or more, and get $ 1.49 a gallon (your container in both cases). I think what I will do is go pickup 20 gallons and one of those plastic livestock feeder tubs. Then I will soak the 350 Chevy engine block I have sitting around and see how it does on that one. If it doesn't damage that one I think it will give Dan the confidence to drop his Olds into the same mixture.

Never thought I would know so much about molasses !

Don