Light rust on bullet mold

[SteveM54]

Opened one of my bullet molds yesterday & found it had a light coat of rust inside & out. Looking for the best idea for cleaning it without doing damage. Would it be better to try putting it in the Ultrasonic cleaner or maybe use a little mix of baking soda & lemon juice? I do have some extra fine steel wool but??????? This picture is only the outside but it's rusty inside also.

[atfsux]

I recently acquired a bunch of molds from a commercial caster who suspended operations 2 years ago. Some of the molds hadn't been used for a few more years than that. So a few of them had this same issue.

In the past, with rusty tools and bolts, I have previously used Evaporust to soak items in to get the rust gone. But I didn't have any on hand just now, so instead I grabbed the CLR (Calcium, Lime, Rust) from under the kitchen sink and poured about an 1/8th of a cup into a small glass. I took a nylon bristle parts cleaning brush (looks a lot like a toothbrush) you can get at any Harbor Freight, and dipped the bristles in the CLR and started scrubbing the molds. It was an ever so light frosting of rust, so it didn't take much, and the rust all scrubbed away after about 5 minutes per mold. The CLR is non-toxic, so I didn't have to worry about getting it on my hands or breathing in any fumes. Out of about 50 molds I needed to clean this way, a small bunch of them (maybe 6 or so) had a slightly heavier speckling of rust. For those, I switched to using the brass bristle brush, so as to be able to scrub a bit more forcefully, but not to scarify or damage the molds. And with relative ease, even those more heavily rusted ones came out nice and clean.

[TurnipEaterDown]

I had a couple iron molds recently that got lightly spotted, mostly w/ a very slight patina in some areas.


Smeared JB Bore Compound on an oversize q-tip like swab sold for cleaning firearms (after stripping some of the fuzz off to just fit snugly, I selected the closest size over the mold), and then spun the swab inside the Closed mold very slowly w/ a cordless drill.

Inspected the corners at the lube grooves closely, and used a small swab w/ JB like a pencil eraser to get the corners, cleaned them up as would w/ a new mold, and they cast like new.

I don't think the JB can really take much off as long as the swab was spun really slowly, so seemed reasonable to me. Maybe someone will pounce on my choices...

[groovy mike]

Cast some bullets with it. The rust will come off.

[uscra112]

Barkeeper's Friend or Bon-Ami have powdered feldspar in them. Will take the fine rust but won't hurt the mould. I also used toothpaste for this in the '50s but don't remember which brand.

Then of course there's the old Coca-Cola trick. (Phosphoric acid in low concentration.) Ditto "muriatic acid" sold for cleaning masonry.

[challenger_i]

uscra112: I believe Colgate Whitening is the flavor you mention.

For surface rust, I have used Kroil as a soak, then flush with carb cleaner. Re-oil after treatment.

Another method of rust removal, borrowed from the antique auto restorers, is 1 part molasses to 9 parts hot water. Soak offending steel component in this solution until clean. (And, from experience cleaning steel aircraft parts, it will be CLEAN!) Flush thoroughly with boiling water, then oil. This method will not damage or distort machined surfaces. When you are done, you may pour the solution on your ant beds and chase THEM off!

[uscra112]

Molasses! At my age I ought to have heard of that one by now, but no.....

Last week was cleaning up a Stevens tang sight, and that might have been very useful. Small parts, tiny crevises, didn't want to use acid or abrasives.

I've done electrolytic for heavily rusted stuff, but it leaves a coating that would not do for a mould.

Mould cavities I've done OK with a bronze bristle bore brush, spun with a handheld drill motor.

For external surfaces on guns, I've discovered "Big 45 Frontier Metal Cleaner" It's a wad of some kind of metal shreds, not steel wool, and it really lives up to it's claims. Wet it with Corrosion-X or something like and scrub away. It really doesn't touch bluing, but it does get the rust off. www.BIG45.COM. Store the used wad in an old medicine bottle - it seems to last indefinitely.

[challenger_i]

Yah, when a close friend recommended molasses for a project I had, I thought he was nuts! However, after having used the process, I am a convert.

Now, what I need is a gentle method for removing corrosion from a set of aluminum mold blocks. I have been hunting for a mold for a 120r .321 32 cal bullet (32-30 Remington) for several years. Finally found one and, when it arrived, it appears to have been a refugee of The Great Flood and didn't make it onboard the Ark.

[uscra112]

I had the same need for a light .321 bullet, for the same reason. Had Accurate cut a mould for me. Cast up a couple hundred bullets, and there they sit. Owing to my advancing age and state of decrepitude I've never had the gun to the range.

nb: Looked it up. Molasses is acidic. https://www.whatistheph.com/substance/Molasses

[gwpercle]

I have always removed the light surface rust with #0000 steel wool , copper wool would also work if you have it ...and any light oil or CLP that happens to be on the bench ... the oil helps the steel wool polish off the rust ...
You want to leave a nice smooth surface where the rust was .
Steel Moulds are fairly tough and a little light rust doesn't harm them if polished away and not pitted in the boolit cavity.

I spray mine with any Dry Lubricant ... the Dry lube protects from rusting and doesn't contaminate cavities or needs to be removed . Been using Liquid Wrench Dry Lube ( L 512 ) either the liquid or spray on works great .
PS- can also be used as a mould -boolit release ... beats Drop-Out Seven Ways To Sunday !
Gary

[blackthorn]

Did this with a couple of free round ball moulds that had surface rust. Warm water and a couple of spoons of citric acid. Degrease, and soak over night and mould will be almost "in the white". It will remove bluing in my experience so---

[45workhorse]

https://www.evapo-rust.com/

IT WORKS, and you can reuse it!

[SteveM54]

Wow, thanks guys. Good info

[45DUDE]

When I get a rusty metal mold I have a sand blast machine and run on 30 pounds with sugar sand. There is no metal removed but you loose the color. You can get the color back by heating the mold up to casting temperature and submerge in your pot a few seconds. The mold turns darker and the lead slides off.

[georgerkahn]

I have had this challenge a couple of times -- both on pre-owned by others' moulds. I sprayed the Dickens on them with G96 -- did not touch them; just left it on overnight. Next day I took clean, dry, paper toweling and pretty much wiped off the rust. Troubling to me was memories of middle-school chemistry, where I was taught that iron -- Fe -- gets oxidized and Fe2O3 -- rust is formed. It is not an even, plane process -- so there'd no doubt be lots of pits. Anyhoos, I repeated the process, and next day's towels came out still almost white? I reckon I wiped off all the rust -- but how about the pits? I honestly do not recall if I used gasoline (shhhh) or lacquer thinner -- one of the two, to degrease the moulds. I then heated them a couple of times and -- no smoking, mould release, etc. -- they both cast awesomely!
What I did.... maybe I was just (in this rare case) lucky?
geo

[wilecoyote]

...if you lightly heat (hair-dryer can work, if you don't have a heat gun) the iron mold after the rust is removed, then you oil it, the lubing will last longer & better_

[45workhorse]

Drop the mold in a covered container full of Evap-o-rust, completely cover the mold let it set for a day or two!
Take it out rinse it off, put it to use. You might have to run brush over it, if it is thick stuff!
It's literally that easy.
When done pour the Evap-o-rust back into the container, ready to use again on other items.

[ShooterAZ]

I've heard that the evaporust rust works really well, but I've never tried it. Many years ago I acquired a large box of older boolit molds at a garage sale that were rusted up pretty bad. I soaked them in white cider vinegar for varying amounts of time, and it did eventually remove the rust without ruining the molds. I'd say it might be a last resort, but it did work out for me. Rinse them well, and oil them down afterwards.

[JonB_in_Glencoe]

I would just use a piece of denim and some oil to rub most of it off, then clean with dishsoap, hot water and tooth brush. Then cast some boolits. The heat will cook out any rust, if there is any in the pores, and also start the heat staining process to build a patina finish.

[JonB_in_Glencoe]

I've heard that the evaporust rust works really well, but I've never tried it. Many years ago I acquired a large box of older boolit molds at a garage sale that were rusted up pretty bad. I soaked them in white cider vinegar for varying amounts of time, and it did eventually remove the rust without ruining the molds. I'd say it might be a last resort, but it did work out for me. Rinse them well, and oil them down afterwards.

I've used the vinegar rust removal method on a large item, too large to dunk. I sanded the item, but worried about rust in the pores/pitting. Adding heat helps vinegar do it's thing. I soaked the rusted steel item then wrapped with shrink wrap (so vinegar doesn't dry), then put the item out in the sun on a 90º day. Every 20 minutes or so, I'd sneak some more vinegar under the shrink wrap. Worked great.