Can an Aluminum mould become "tinned"

[JWFilips]

I'm trying to figure out what happened today. I was using my Lee two cavity 452-230 TL mould which I have already cast probably about 2000 boolits with with out a problem ( It is a new style with alignment pins and has worked well from day one with out any special leementing...just a good scrubbing before first casting.) Well today everything seemed to be normal however I started to notice The boolits in the forward part of the mould were hanging up & not dropping well unless I had to beat on the handles....this seemed very strange for this mould which I cast a lot with. Those bullets that came out appeared to have indentations near one side of the mold half.

I finally shut everything down and when the mould cooled down I checked it out with a 20X loupe There appeared to be lead deposits in the TL bands next to one edge of the mould This was why it was hanging up and leaving notches in the boolits It appears to be lead deposits but I can't imagine this happening on an aluminum mould ( I know this can happen with brass moulds) Is this possible?

[Dusty Bannister]

Overheated mold? Dropping the casting while too hot?

[Jailer]

I've had that happen to one of my molds. Get it good and hot and it should wipe away with a cotton cloth.

[JWFilips]

Overheated mold? Dropping the casting while too hot?

Well possibly so. I have recently be working with a large brass mould ( learning that it needs a lot of heat) and I may have inadvertently got this small aluminum block mould too heated accidentally when I switched over to it.

When I first saw it I thought the mould got mashed somehow. Didn't know lead would stick to the aluminum blocks. Will do the heat and wipe thing today Thanks

[btroj]

I don't think it is tinned. I think bits of lead get held mechanically in vent lines and slowly build up. I find that they are pretty easy to remove.

[JWFilips]

I've had that happen to one of my molds. Get it good and hot and it should wipe away with a cotton cloth.

Thanks for the tip. Heated it up and wiped it all out this morning ( more lead then I thought) used Q tips Now it looks like new.
I'm always learning something here!

[uscra112]

You can solder aluminum by using the right kind of flux, but it would not almost impossible to get such flux into your mould without a concerted effort.

[detox]

Sounds like you may have a burr. I would lightly polish cavity with JB bore paste, bore brush and cordless drill.

BTW are your cast bullets concentric with no mould offset? Receading alignment pins maybe...i have seen this happen gradually with a new 2 pin lee mould.

[CGT80]

I ran into this problem with a new NOE aluminum mold. I tried using toothpicks to remove the build up when the mold was hot. It has been soaking in aerokroil for a few days and I will give it another go. I read here that some people think oxides can build up, and they are harder to remove. My mold didn't clean up easily. If the kroil doesn't work, I will try using some boolit lube on the heated mold, as suggested on this forum. I wondered about polishing with toothpaste and a boolit, but I hate to even take a brass brush to a new aluminum mold. I am not experienced with this issue.

My boolits were sticking and they had little bit of lead missing at the parting line of the boolits. I did get some of the material cleaned out and they dropped better, but I still have more work to do. I haven't tried pop sickle sticks yet. I suppose a wood dowel would do as well.

[MtGun44]

Tinning is actually wetting the metal and bonding. Does not happen with aluminum
due to the layer of aluminum oxide on the surface.

Smearing lead mechanically onto the aluminum, can and does occur not the same as
tinning, far easier to remove. Lube with Bull Shop lube and cast - the smears will
slowly go away, usually gone 1/3 of the way thru a casting session.

Bill

[JWFilips]

My boolits were sticking and they had little bit of lead missing at the parting line of the boolits. I did get some of the material cleaned out and they dropped better, but I still have more work to do. I haven't tried pop sickle sticks yet. I suppose a wood dowel would do as well.

Yes that is exactly what was happening to me.....That is when I checked it with a high power magnifier and saw the little pieces of lead stuck in the bands near the mould edges That tip about heating the mould up ( I used a propane torch) and wiping the bit of lead out worked well but you do have to bring the temperature up pretty high before the lead released.
BTW I would not use a brass brush on an aluminum mould .......Don't ask me how I know:smile: