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Thread: Aluminum molds don't rust...

  1. #1
    Boolit Master
    Join Date
    Sep 2016
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    610

    Aluminum molds don't rust...

    but their steel fittings can and do.

    I thought I'd done right by my molds by coating the sprue plate with Sheath and oiling the hinges well prior to storage. This has worked for my aluminum molds before, but when I took a couple of matched molds out for a casting session after couple or three month break, the sprue plates had rust on the edges and especially around the hinge bolt, whose bearing sheaths and wave springs were nearly frozen together

    I think the problem is that the last session was the first time I used both molds for speed casting, where the sprues were water cooled on a damp towel after each pour. I guess water/steam worked its way into the hinge where the heat of sprue plate wasn't enough to evaporate it all as the mold cooled, and the oiling didn't penetrate enough to displace the moisture.

    So once I manage to clean off all the rust I can go back to speed casting, but I'll have to disassemble, dry, relubricate and reassemble the fittings every time.

    Live and learn...

  2. #2
    Boolit Buddy Randy Bohannon's Avatar
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    All of my moulds regardless of material they are made of get treated the same. While mould is hot and I am done I use a piece paraffin wax and melt it all over everything, screw holes, inside,outside. When the mould is hot it penetrates and gives everything a nice thin coat of wax.When cooled they are perfectly preserved. I use a metal electrical box on a hot plate to pre heat the mould, it melts and burns off the small amount wax that was left.

  3. #3
    Boolit Grand Master
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    For short term storage (less than a week) the molds get a little bit of Kroil applied to the holes of the sprue plate while the molds are still warm. The molds are generally left attached to the handles.

    For Long term storage [more than a week]:
    When I'm done casting but while the mold blocks are still warm, I place a small dab of grease [RIG] on top of each hole on the sprue plate. The heat melts the grease and it flows into the cavities. At that point there is no moisture present due to the heat of the material. The grease flows and covers most of the surfaces at that point. When the mold cools to the point that I can handle it, a clean patch is used to spread the grease over all of the surfaces that didn't receive grease, mostly the exterior portions of the mold blocks. The result is a mold that has a thin layer of grease on all surfaces, including both sides of the sprue plate.

    The key to both of those methods is to apply the oil or grease while the material is still warm.

    With that method I've never had a rust problem. The mold does have to be degreased when put back in service but that's the price you pay to prevent rust.

  4. #4
    Boolit Master


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    I spray mine down with Ballistol after use and spray them with brake cleaner before using again. I haven’t had any problems, but they are stored in a dry environment too.

  5. #5
    Boolit Grand Master

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    Quote Originally Posted by GregLaROCHE View Post
    I spray mine down with Ballistol after use and spray them with brake cleaner before using again. I haven’t had any problems, but they are stored in a dry environment too.
    This is pretty much what I do. I also wrap them in an oily rag and store them in an airtight box. I recently bought an MTM dry box just for mold storage and I keep it in the house in a controlled environment.

  6. #6
    Boolit Master RED BEAR's Avatar
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    i use a silicone gun oil never had a problem. some molds are stored for years at a time. be careful using kroil ( perpetrating oil ) for short term its fine but if left for long periods it will gum up and start to harden.

  7. #7
    Boolit Grand Master

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    While aluminum doesn't rust it can still corrode from things around it so a protective coating is a good idea.

  8. #8
    Boolit Master

    gwpercle's Avatar
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    I made a decision a long time ago to keep water away from my moulds. I clean with acetone and air cool by placing a hot mould in front of a small fan while filling the second mould.
    Water and moulds do not mix.....as careful as you are the water will come back to bite you !
    No water, no way, shape or form,
    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  9. #9
    Boolit Buddy
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    Dec 2005
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    I keep all my moulds, steel and aluminum in a large steel G.I. ammo container (it is either for .50 cal. or some small cannon...larger than .30 cal. ammo cans), with bags of silica gel to absorb the moisture, in my unheated garage, here in Michigan for more than ten years without any rust. There is no need to leave a bullet in the cavities...no need to oil the moulds...no need to put preservative on them. Some of you guys just work way too hard.

  10. #10
    Boolit Master
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    Sep 2016
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    I think that I will also use air tight ammo cans with VCI inserts as part of my post casting mold care and storage. I had not gone that way originally because I wanted to leave the handles on the frequently used molds. Maybe I can scare up a 20 mm ammo can (those have the sealing O ring too, don't they?).

    I may have only a fraction of the mold collections of some on this forum, but mine still add up to a fair chunk of change and I want them to last.
    Last edited by kevin c; 01-03-2019 at 01:21 AM. Reason: Additional thoughts

  11. #11
    Boolit Master
    Mal Paso's Avatar
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    I keep mine in the roll-away tool chest in the livingroom, never had a problem.
    Mal

    Mal Paso means Bad Pass, just so you know.

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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