Cleaning Corroded Moulds

[Ricochet]

I've been working on moulds that got damaged sitting on a basement shelf when a toilet started leaking and dripping the nasty water straight down on them, for a long time before I discovered it and got the problem fixed. It just made me sick to see what it had done to them. :x The worst were my Lyman #457122 Gould HP and #429244HP that I had bought new and kept pristine. They were covered with a thick lumpy crust of red rust. Another new set of Lyman blocks I haven't even used yet, a 2-holer #358429, had some light blotchy rust that didn't involve the cavities. My Ideal #452460 and #358432 were rusted all over inside and out, but a light uniform coat, not nasty like the hollowpoints. My Lee aluminum moulds were a mixed bag, some affected little if at all, some with mostly cosmetic rust on the handles and white patches on the blocks, and four that got a lot of corrosion on the blocks. The worst is a custom 6-hole #311291, a much used favorite for my .30 calibers and not easily replaceable. The steel handle parts rusted badly, the anodized sprue plate has white patches on it, and the blocks have heavy crusty white corrosion. It's especially bad on top of the blocks under the sprue plate, thick and lumpy enough to interfere with proper smooth close fitting of the sprue plate. The mating faces of the blocks have a lot of corrosion on them, but there's not much in the cavities. Several wooden handles and the HP pin knobs lost their finish, and some ferrules rusted badly.

The iron blocks were pretty easy to clean up. I boiled them and rubbed off the loosened rust, a rough rust blue job. They'll never look new again, having substantial pitting on the outside of the HP blocks, but the cavities have no more than a velvety appearance with no major pitting. The HP pins did pit pretty badly. Overall they're still quite usable and should make good boolits.

The aluminum blocks are another matter. I tried boiling them like the iron blocks while I was at it, but that did nothing to loosen the hard white corrosion. I thought about trying soaking in vinegar. I've looked online for recommendations on cleaning up aluminum corrosion but haven't found anything very encouraging. I know that hydrochloric and sulfuric acids can dissolve it, and sodium hydroxide will vigorously attack it, but it would be easy to damage the cavities. Straight abrasive cleaning risks messing up the flat machined surface that the sprue plate works on. I'm thinking of trying mag wheel polish, a paste containing some hydrochloric acid and a fine polishing abrasive, and just rub the heck out of it with a cloth.

What have you found to work well to restore corroded moulds, especially aluminum ones?

[Greg S]

Just spit balling here....

If the Aluminum interiors are good, how about some nail polish to seal the surface inside the cavities and vent li es ect before cleaning with caustic solution(s).

[Ricochet]

That's a good suggestion, thanks. I'd thought of swabbing the cavities with grease, which of course would have to be cleaned out later.

[masscaster]

Get a jug of CLR. It will take the finish off of Iron, but it's better than rust.
Use a soft toothbrush to clean the cavities and handle channels.

Jeff

[labradigger1]

Iron molds, use evaporust.

[Vann]

Evaporust as stated above is great, there is also a white rust remover made by Loctite, not sure of the name but it's supposed to remove the white corrosion from aluminum.

I just came across it one day while wondering around a hardware store. Never tried it though.

[Gtek]

On the Lee's what about a mag wheel cleaner, I know Alumiprep 33 would get after it. The iron ones I have went after I layed in a pool of OSPHO and scubbed with stiff nylon brush then cold blued when done. Sorry for your luck and that you were poo'd on, I keep mine in Tupperware kind of stuff due to a fear of anything but me touching them.

[Victor N TN]

Sorry for your luck and that you were poo'd on, I keep mine in Tupperware kind of stuff due to a fear of anything but me touching them.

Good idea. I may have to do the same. I had an insurance settlement several years ago. I bought a new RCBS furnace and 5 new molds. I just haven't been able physically to get it done.

Thanks again for the Tupperware idea. I think I need to invest in something like that myself.

[44man]

An old machinist I bought a lot of stuff from would use Tupper Ware and put a chunk of camphor in each box. Nothing ever rusted. But you have to wash a mold before use.

[labradigger1]

For storage of my iron molds I wrap them with Vci paper, leave a bullet in the cavity, write the alloy used on the Vci paper and store them in 6 different Tupperware molds above the electric base board heater in the loading room. By leaving the bullet in the mold the theory is rust and the boolit can't occupy the same space as there isn't room for it, the other reason is I can remove this boolit and check as cast size, weight and hardness and refer to the alloy written on the Vci paper and repeat or modify as needed.
My .02

[duckey]

I've used Naval Jelly on steel molds and it worked slick.

[Ricochet]

Good ideas. Thanks! Tupperware would have prevented my problem. I have CLR and should have some mag wheel cleaner if it hasn"t dried in the package over the last 25 years or so. Read that the Naval Jelly folks make an Aluminum Jelly that sounds worth looking into.

[44man]

0000 steel wool can clean a lot with no damage either. I always spill a little Hoppe's on it.

[lightman]

If you do a search on Hensley & Gibbs molds one of the sites has a good article on cleaning molds. Dish soap and a tooth brush are recommended. I might even do the tooth brush with some Kroil. The main thing is don't get too aggressive.

[Echo]

Evap-O-Rust gets my vote. I have used it often, and keep a mason jar 3/4 full on the sink counter. Just open the sprue plate 180 degrees stick it in the jar for an hour or 2, and Voila! But - Only 2-cav molds this way...

[Ricochet]

0000 steel wool wet with kerosene is what I card off rust biuing with and that's what I did on the iron moulds.

[Ricochet]

If you do a search on Hensley & Gibbs molds one of the sites has a good article on cleaning molds. Dish soap and a tooth brush are recommended. I might even do the tooth brush with some Kroil. The main thing is don't get too aggressive.
Being too aggressive on the aluminum is what I want to avoid. I haven't done anything yet. I'm weighing all the options.

[JoeH]

Evaporust as stated above is great, there is also a white rust remover made by Loctite, not sure of the name but it's supposed to remove the white corrosion from aluminum.

I just came across it one day while wondering around a hardware store. Never tried it though.

I always enjoy "wondering around in a hardware store", finding stuff I never knew existed and even some things I don't know why they do exist.
~

[Ricochet]

I tried a bit of hand rubbing with CLR on a towel. No joy. Now I have it soaking in diluted CLR. Not doing much yet. I'll let it go overnight. I'll probably end up using the 0000 steel wool and kerosene.

[Ricochet]

After 24 hours soaking in diluted CLR it doesn't look a bit different. But the big scabby white crusts are softer and I'm able to scrape some of it off with a thumbnail! I put it back in soaking. Tomorrow I'll get out the 0000 steel wool and use it gently.

[Rooster]

Following this thread as it is germane to my interests. Thanks Ricochet!

[Ricochet]

You're welcome, Rooster. I figure lots of people have dealt with similar problems. I have good news to report. After soaking the badly corroded Lee mould for 48 hours in the diluted CLR it really didn't look different. But there was quite a pile of rust in the bottom of the container. The white crust on the aluminum was quite soft, and a little work with the 0000 steel wool and kerosene got it off. There was deep pitting left. But it doesn't involve the cavities. The rusted pins and sockets now mate freely, the moving parts move, and the sprue plate fits closely and slides freely. It looks "vintage" as they say on eBay, but will cast good boolits. I'm happy with that. :D