Vinegar or Molasses to make cast iron look foundry fresh?

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Demonic

Demonic

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There’s a bunch of references and topics on here, but is one soak better than the other? I’m getting ready to do a couple of blocks, for myself and friends. Is one less likely to goof up a machined surface? Do you get less flash rust w one vs the other? Replies with experience and pics appreciated.
 
I have tried the vinegar method. Looked like it removed the rust. But days later rust returned worse than it was. I hear you need to kill the vinegar with something like baking soda
 
I've always taken my blocks to a machine shop for cleaning and machining and they come back looking like new. I'm not sure what they use to be honest.
 
RAT ROD AL said:
I have tried the vinegar method. Looked like it removed the rust. But days later rust returned worse than it was. I hear you need to kill the vinegar with something like baking soda
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I think any chemical process that removes rust should have the parts passivated/neutralized after the de-rusting process. Baking soda solution is good for neutralizing acidic solutions. Once clean, oil or seal the parts to prevent additional corrosion. Just about any oil or grease will work if you seal in a plastic bag, which limits exposure to oxygen.

I've used vinegar with very good results. Cheap to do and easy clean up. I've never tried molasses but supposedly you need to use farm grade, not the stuff your wife is using to bake cookies.
 
I have a 50 gal vat of white Vinegar that I use to clean rusty parts. They need to be submerged for 48hrs and then neutralized with baking soda or Windex. Vinegar will continue to etch if its not neutralized. Parts clean up nicely with a wire wheel.

Vinegar will not penetrate grease. For an old motor it would be best to have it hot tanked and blasted by a shop.
 
Just Send It said:
I have a 50 gal vat of white Vinegar that I use to clean rusty parts. They need to be submerged for 48hrs and then neutralized with baking soda or Windex. Vinegar will continue to etch if its not neutralized. Parts clean up nicely with a wire wheel.

Vinegar will not penetrate grease. For an old motor it would be best to have it hot tanked and blasted by a shop.
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What ratio of baking soda to water do you used to neutralize the vinegar. Thanks.
 
I've used naval jelly which is the same sort of acid as vinegar before. It only took a few seconds for flash rusting to occur so I avoid it as much as possible now
 
ACME SS said:
I've always taken my blocks to a machine shop for cleaning and machining and they come back looking like new. I'm not sure what they use to be honest.
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There’s 1 main cleaner used in the parts “dishwasher” which is Safety Kleen’s water based solvent. The “dishwasher” is heated to about 180 degrees with high pressure nozzles that was the parts. Of course that is still old school solvent tanks, but most places now use the water based solvent tanks/parts washers. Here’s a pic of one style.

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Every engine is hot tanked, Then washed, All passages are scrubbed , Then dried with heat, Then glass beaded with polish grit, Then it is put in a tumbler to empty the block of any dried dirt or grit, All threaded holes are chased, Then sprayed down with WD40 to prevent rust while waiting for machining, When the work is done it is cleaned again and stretch wrapped.. You can never clean to much.

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Look around and see if you can find a shop in your area with a laser cleaner.

Laser cleaning is making all other forms of cleaning and rust removal obsolete.

And it doesn’t affect the surface like glass beading and shot blasting does.
 
I've never done anything as big as a block as far as rust removal goes... but I've cleaned plenty of parts with vinegar. Depending on how crusty it may be, you might need to add a little elbow grease. I've brought a 8.75 center section back to life after it had been sleeping outside for 20+ years. I left it in white vinegar for about 3 or 4 weeks, and about every couple days I would take it out and hose it down with a little pressurized water ( regular garden handle on the jet setting) to knock off any loose gunk and then back into the vinegar. At the end it all looked brand new BUT it will begin to flash rust in minutes. For small parts like hand tools I've scored in garage sales I just have a couple of tubs where I clean parts off in water first to get all the vinegar off and leave them clean, then straight into motor oil (I always have a little 0-20 synthetic laying around that is excess from changing the oil on my wife's car) The tools end up amazing for a long time after allowing them to dry in the sun. For a full engine block, with all the internal passages and cavities. I would highly recommend just taking it to a shop and having it done professionally. They invest a lot of money into special machinery for a reason.
 
Rat Bastid said:
Look around and see if you can find a shop in your area with a laser cleaner.

Laser cleaning is making all other forms of cleaning and rust removal obsolete.

And it doesn’t affect the surface like glass beading and shot blasting does.
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My brother was looking into one and he uses one at a friends shop. The problem when them doing blocks is you still have to bottle brush the passages. There great for surface cleaning.
 
Rat Bastid said:
Look around and see if you can find a shop in your area with a laser cleaner.

Laser cleaning is making all other forms of cleaning and rust removal obsolete.

And it doesn’t affect the surface like glass beading and shot blasting does.
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double 0 glass beads do not etch metal if they are new clean beads. They actually polish the metal. The guys that leave the beads in for many jobs dull the metal. I clean plastic , brass, aluminum, and copper. The most important is cleaning the beads out of the crevices when you are finished. . Never glass bead items that have not been degreased and dried. I use Glass beads for parts . and crush glass for auto body. Sand and zinc oxide is for iron workers, Beam and bridge cleaners.
 
Scody21 said:
There’s 1 main cleaner used in the parts “dishwasher” which is Safety Kleen’s water based solvent. The “dishwasher” is heated to about 180 degrees with high pressure nozzles that was the parts. Of course that is still old school solvent tanks, but most places now use the water based solvent tanks/parts washers. Here’s a pic of one style.

View attachment 1716030464
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Thats the EXACT unit we had where I worked. You get the water to soap mixture off, which happens from evaporation over time and you can find yourself with a foam apocalypse LOL.
 
Oldmanmopar said:
double 0 glass beads do not etch metal if they are new clean beads. They actually polish the metal. The guys that leave the beads in for many jobs dull the metal. I clean plastic , brass, aluminum, and copper. The most important is cleaning the beads out of the crevices when you are finished. . Never glass bead items that have not been degreased and dried. I use Glass beads for parts . and crush glass for auto body. Sand and zinc oxide is for iron workers, Beam and bridge cleaners.
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Ok, and the laser cleaners make sand blasting obsolete. Look at all the hoops you go through to get something clean.

Ive seen the laser work in person. Like I said, the glass bead machine is obsolete.
 
I've used Electrolysis, Farm Grade Molasses & Water, but the best way if you're only doing one block is to just take it to a shop. Much easier and cheaper in the long run.

Now if you intend to do other parts and like fooling around with stuff at home I would highly recommend what my AMC friend Rick Jones does using Citric Acid.

Here's the link to the AMC forum article where Rick posted a detailed write up with lots of photos.

Derusting an engine block

In my opinion the first thing one should do in cleaning a block is to pour the water jackets full of vinegar for a few weeks to let it eat away and loosen the lime buildup that settles in the

bottom of the water jackets. Then a trip to the car wash or use a power washer in all the holes you can get it in to help flush the lime out. After that process you can use any other

method to deal with rust and oil buildup you like.


I should also note that using the Farm Grade Molasses and Water method only eats the oxide (rust) and does nothing to eat on the other surfaces like acids do and does not need

anything other than a simply rise of water when finished with the process unlike using an acid that requires a Baking Soda rinse to neutralise the acid. However it will not attack oil like

an acid will. Another FYI with using Baking Soda is it must be cleaned off really well or it will cause puck marks in the paint every place a particle is left behind. I learned that one the

hard way.

Tom
 
ACME SS said:
Thats the EXACT unit we had where I worked. You get the water to soap mixture off, which happens from evaporation over time and you can find yourself with a foam apocalypse LOL.
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We turn the heater off. So one morning I forgot to turn the heater on, so yeah cold water is a no go… The best flood, this past summer my brother was running a motor on the dyno late at night, and his setup right now does not save the water after it drains from the brake, so his dumbass forgot to turn off the water to the 2000 gal tank, which feeds off a 2” main. (He pulled the float valve to replace, this this wasn’t in-place) So he pulled into the parking lot to find it flooded out and then half of his shop flooded out with a major waterfall off the top of the water tank… #rookie
 
Scody21 said:
We turn the heater off. So one morning I forgot to turn the heater on, so yeah cold water is a no go… The best flood, this past summer my brother was running a motor on the dyno late at night, and his setup right now does not save the water after it drains from the brake, so his dumbass forgot to turn off the water to the 2000 gal tank, which feeds off a 2” main. (He pulled the float valve to replace, this this wasn’t in-place) So he pulled into the parking lot to find it flooded out and then half of his shop flooded out with a major waterfall off the top of the water tank… #rookie
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What is your status??? Get off the schnide and let’s get your stuff on the pump.
 
Rat Bastid said:
What is your status??? Get off the schnide and let’s get your stuff on the pump.
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Scody21 said:
We turn the heater off. So one morning I forgot to turn the heater on, so yeah cold water is a no go… The best flood, this past summer my brother was running a motor on the dyno late at night, and his setup right now does not save the water after it drains from the brake, so his dumbass forgot to turn off the water to the 2000 gal tank, which feeds off a 2” main. (He pulled the float valve to replace, this this wasn’t in-place) So he pulled into the parking lot to find it flooded out and then half of his shop flooded out with a major waterfall off the top of the water tank… #rookie
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Call me tomorrow let’s get going on this if you are ready. I am.
 
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