De-Rusting the cavities of an H&G mould

[FISH4BUGS]

I just bought an H&G 8 cavity mould "as is". I bought it CHEAP so I thought it might make a great "project"mould. It was pretty rusted at some point in its life....probably not all that long ago.
First, it is all there. Handles are solid. It seems to close tightly with no serious hangups on the alignment pins. Unfortunately the guy I bought it from had taken a wire wheel to the outside of the mould.
For that act of heresy may he burn in hell for an eternity.....but it is what it is. I can live with a bright shiny outside of a mould.
Here is the problem: there are a few cavities that have a very light rust in them. Nothing serious but the surface rust is there.
I'd like to do something to remove the surface rust (again, very light) in those places where it exists.
I am soaking the cavities in WD40 to soften the rust.
Any suggestions on how to best remove this rust? I'm willing to put in the time to do it a slowly and do it right.
If I succeed, I will have a (hopefully) great casting mould.
Tips and tricks would be most appreciated.

[Devon]

Electrolysis gets my vote. I used it to de-rust a huge Wilton vise that I found buried in a flower bed. Weighs over 100 pounds. It took a large tank. A mould would be easy peasy. Do a google search for instructions.

[farmerjim]

I used toothpaste and a toothbrush and light brushing on an old Lyman 4 cavity.
Dried it up and started casting. It casts boolits as good as the day I got it 55 years ago.

[darrondb]

Evaporust. Great stuff for light rust.

[BK7saum]

Evaporust should work. Available frim walmart and harbor freight.

[lightman]

I just used Evaporust on some neglected dies. It worked as advertised but it will remove blueing. I probably would start with some Kroil and a tooth brush. Thankfully that previous owner did not use his wire brush on the inside! Good Luck in making this mold work again!

[John Boy]

there are a few cavities that have a very light rust in them. Nothing serious but the surface rust is there.
A 50:50 mix of ATF and Acetone
Let soak to loosen the rust and then scrub with a brass brush

[texassako]

You can spot treat with evaporust by using shop towel pieces in the cavities, soaked in it. I have done it to keep blueing intact.

[Bent Ramrod]

If the rust is light, with no pits, you might try boiling the mould in water. This will loosen much of the surface rust (a toothbrush helps here as well) and turn the nonremovable rust to black oxide, i.e., “rust blue.”

Or, you can just start casting with it. The boolits might be a little “frosty” looking, but generally, IME, shoot fine. The heat of casting will also “blue” the surface rust and stabilize it. The brushing one does afterwards to clean up lead smears and spots will remove the loosened rust.

I’ve done several moulds each way with success. Best of all, neither of these procedures will do anything negative to the mould, and if they don’t work satisfactorily, you can then go with Evaporust or Liquid Wrench and toothbrushing and take it out that way.

Doesn’t work with the heavy rust that leaves deep pits, though. Repeated treatment with Evaporust or penetrants and brushing is the way to go there. Or, if really bad, lapping by hand.

[blackthorn]

You can soak it for two or three days in water with citric acid added. Like evaporust, this will also remove bluing.

[edp2k]

Absolutely use Evaporust . Perfectly safe, works in a few hours, rust just wipes off.

[.22-10-45]

If you can find one of those wooden typewriter erasers..with the little brush on one end..they work fine for mould clean up..will remove rust but will not scratch..I should have stocked up back in the 70's.

[texassako]

If you can find one of those wooden typewriter erasers..with the little brush on one end..they work fine for mould clean up..will remove rust but will not scratch..I should have stocked up back in the 70's.

Hmm, that reminds me of the bundle of bamboo my wok came with to clean it. I wonder if a bamboo skewer, possibly with the end crushed, could be used to scour the cavity of rust without scratching.

[Gewehr-Guy]

I've cleaned a couple of really ugly moulds by using Kroil to soften the rust scale, then used some little scrapers made of brazing rod, I hammer them out like a little chisel and sharpen with a file, and just start scraping. The Evaporust sounds like a good product I'll have to try.

[William Yanda]

I had a Lyman round ball mold with a little rust in the cavity, I used a pencil eraser to erase the rust.

[rondog]

I'll beadblast it for ya, if you wanna pay shipping here and back.

[yeahbub]

I had a few molds that sprouted some surface scale some time back. The ones with light surface rust I cleaned up with Lime-Away back when it still contained phosphoric acid. Naval jelly also contains it, but I wanted a liquid rather than a gel. Evaporust should do a fine job. In the RB mold that had an anomalous tumor of rust growing out into the cavity, I expected to wind up with a pit if I chemically removed all traces of rust, so I lapped it smooth and left the rest of the rust as the wall of the cavity at that location. It flaked a bit with use, but the castings don't show any positive material.

[FISH4BUGS]

There is a wealth of knowledge on this site, and having been here for almost 13 years, I have to say I have never had a question go unanswered.
Many thanks to all.
EvapoRust it is. The local ACE Hardware store has it in stock and I'll pick one up.
Donald

[robert12345]

A good rust remover, ( the folks here seem to know ) ..then rub the lead off, with a lead pencil...

[.22-10-45]

I have used a 1/8" piece of wood dowel with end tapered down to fit in grooves, & used JB compound to clean them up also.

[nicholst55]

Evaporust. Great stuff for light rust.

^^This^^.

[dkf]

If it was me I'd use the Evaporust to soften and remove as much of the rust as possible. Then cast some bullets, drip/tap the base of several for a screw and then lightly lapp each cavity (turn lapp with a drill) with some fine 400-600 lapping compound.(same amount of seconds for each cavity) The lapping will help smooth out any rust and pits. Iron molds take a lot of lapping with courser compound to change the size so you really do not have to worry about it with fine compound and a short amount of polish time.

[gregtu]

Anyone tried CLR, available pretty much anywhere. I haven't used it on a rusted mold yet, but it has worked well on other rusted metals for me.

[quasi]

I apply BullPlate to the rust, let it sit for 5 minutes and scrape off the rust (or lead) with a chop stick.

[gwpercle]

Another vote for Evapo - Rust Super Rust Remover.
Back in the dark ages long soaks in kerosene were used...Evapo - Rust works better.
Scrub with firm bristled toothbrush...avoid wire wheels like the plague.

[FISH4BUGS]

I took a long hard look at EvapoRust and Naval Jelly.
I went with naval Jelly and it seemed to work nicely.
There is still just some minor rust in the cavities that will come out with some elbow grease and some steel wool.
The mould looks awful but the cavities will probably come out just fine. The bad areas are on the drive bands which will be taken out at resizing anyway.
This just might work out!

[Sled]

I’ve started on my rusty moulds with Kroil but will likely need som navel jelly. The good thing is the cavities look pretty good as all the moulds I have were stored for 20 years, in Arizona. And loaded with lead.