Pass in review, dear friends! [Check your stored molds for rust...]

Elric

Elric

Well-Known Member
I am re-creating my list of TPs, molds, and sizers [after my system crashed in Aug of '23]. Finished my TPs, and that took so little time, I went and listed my molds.

Almost all of my molds are stored in two MTM AC30C-11 - Ammo Can 30 Caliber - Short plastic ammo cans, the half-height ones. Imagine trying to heft a full size ammo can, even for the 7.62mm, if it was full of molds... The bottom of each MTM can is lined with VPI. I had one mold with noticeable surface rust. Why, I dunno. There are about 20 plus molds in each can, and almost all molds are rust-free.

In theory, using a sealed ammo can with a gasket, lining it with VPI paper, and having all molds dry after use, should eliminate rust. Maybe I had this one lying out and then stuck it in the can... Dunno. But it is far better to wipe the surface rust off with WD-40, CLP, or RustePrufe and then return to storage.

I prefer the MTM ammo cans over the metal military surplus. The MTM cans are hefty, well sealed, the end latches are easier to use than the military versions, the lid doesn't come off as easy as the military versions and the rounded edges certainly are nice. These two have been in my basement for probably ten years. Love 'em.
 
Last edited:
what brand was it?
we were just having a discussion on another thread about Iron vs Steel molds. One that I had that rusted was late Balisti-cast and I suspect they used a tool steel or something? instead of Grey Iron, like many others use.
 
NW Ohio, rapidly/drastically changing temps, humidity, condensation literally DRIPPING off cool stuff in the garage when you open the door to sultry conditions of the next day, hour, minute...

All my tools in the garage are fine - always have been. I've let iron moulds set out in it without any form of protection between casting sessions, which could span weeks.

Then, one day, out of the blue, RUST! On ONE oiled mould (out of several dozen) sealed in a defunct freezer with five pounds of dessicant bags.


No idea why. It happens once in a great while and I clean it up and trudge on.
 
I have a genuine hatred for rust, and it is an unrelenting enemy.

The key to preventing rust is preventing oxygen (air) and water (even water vapor) from reaching the surface of ferrous metal. There are dozens of methods to accomplish this but the simplest is a barrier of oil or grease on the metal to protect it.

Airtight containers limit the amount of air (oxygen) inside the container. An appropriately sized container that has little extra air space available when closed is preferable to an excessively large, nearly empty container. And an airtight container will also prevent the intrusion of water vapor into the interior.

Just about any oil or grease will prevent rust but what makes one superior to others is its ability to remain over long periods of time. Some oils or grease will dry, harden, gum up, evaporate, or otherwise degrade and fail over time.
 
VPI paper has a shelf life.............. reason why I don't use it to store my pocket knife collection.
 
Moulds stored in a temperature-controlled environment should have the best chances too.

Mine are stored in my shop, which may as well be outside. The freezer I store them in prevents wild temperature swings, but can still be a bit of a hazard. Any metal of significant mass which is subject to a night of sub-freezing will stay cold longer than metal of less mass. We get several days a year where it will freeze at night and the next morning becomes warm and humid. If you open the garage door, everything inside that is cold will condensate as soon as that warm, moist air wafts in.
 
Airtight is a misnomer in most cases. Lots of ways to minimize moisture laden air from getting into a closed container, but short of a welded seal on a metal container, none are perfect. And even then they have to be tested with helium to ensure a complete seal. The problem is the "pumping" that occurs with temperature and atmospheric pressure change. A good elastomer seal will minimize the seepage but not completely eliminate it. Keeping the airspace to a minimum as @Petrol & Powder mentioned is important. Plastic containers can be useful but all plastics are permeable to water vapor to some extent.

Another factor is the variation in corrosiveness of skin oils etc. I don't have a problem with my "fingerprints" causing corrosion, but my son does. If he handles anything metal of mine I'm careful to wipe it down with an oil rag.
 
Mine is a slow painful learning experience. Rust just literally wasn't a thing on anything but water fouling gear and lug nuts on boat trailers with hub caps and manual hub 4×4 with cut out hub caps . 3-3.5" of annual rain and no humidity will do that though .

Like those above I'm not a corrosive sweater , more an oiler really. So far om packaging and VCI is doing the job in the house where the safe hovers around 38% in central west AR . I've had to clean up that H&G twice in the 6 years here usually about the first of June I go through everything and dampen the oils . I lost the Blockade in the big move or I'd be using that at least on the handles and outsides .

Whether right , wrong , or lore , I've not taken to leaving the last pour in the moulds , although I do have a couple of participants in a study .......no results yet , so I guess that means it makes no difference.
 
We have fairly low humidity here much of the time, so rust is a minimal issue on iron and steel alloys. Kalifornistan has its share of downsides, but humidity isn't one of them--thankfully.
 
yep leave in the drawer or on top of the pot or on the bench....
i left all my molds, lube sizers, pot's etc. in a pull behind trailer for about 5 years when i first got here.
i may have sprayed them with some wd-40 once,,, or not, i don't remember.
 
Evapo-Rust. I -assume- you are concerned with rust on the inner faces of the mould halves. Get a shallow plastic tub, splash in enough Evapo-Rust to cover the sides that need it [maybe all of it...] and put the halves in it. The chemical reaction will remove ALL rust, that includes bluing. If there was pitting, the pits will be totally bare.

Once the rust has been removed, the used Evapo-Rust can be flushed down a drain [non toxic!].

The metal is totally bare! Wash it off, you can use a oily cloth to protect it, but the oil will have to be burnt off before casting good bullets [nothing unusual]. Once you heat up the treated blocks while casting, they will heat blue and protect the blocks.
 
Last edited:
When I discovered my Ballista-cast iron/steel mold rusted, stored about a year in a supposedly air-tight container. I used a denim cloth and oil and hand rubbed all the surfaces of the mold, to remove the rust ...being careful of the cavities ,,,I was lucky, not much rust in the cavities. Then I cleaned it with toothbrush, dish soap and hot tap water. The I fired up the pot and cast a bunch. I was satisfied with the results, so I coated it with kroil and put it in the air tight container for storage. From that point on, all my Iron molds were stored with a coating of kroil.
 
You must log in or register to reply here.