Pot Metal at High Temperature?

[Strelok]

Hey there.

I'm hoping to refinish my RPK with a matte-black engine enamel. Most of the gun is steel, but small parts such as the bipod swivel, front sight and gas block are a pot metal of sorts.

The curing process requires the painted metals to be baked or 'heated' for about 40 minutes. I keep hearing that high temperatures will damage what little strength the pot metal already has and become brittle. Is this true?

Any help is appreciated.

[DarkAngel]

Depending on the elements used in the pot metal, the melting point would vary, so noone can give you an exact temperature, or even a suitable range unfortunately without knowing the exact composition

Heat guns work in a pinch, but i wouldnt be too sure about using anything hotter as heating pot metal (while it may not actually "melt" the metal, it may cause it to deform or change size/shape.

Im not a metallurgist and ultimately its up to you, but I dont recommend it.

[Kingsix]

Originally Posted by Strelok

Hey there.
I keep hearing that high temperatures will damage what little strength the pot metal already has and become brittle. Is this true?

Any help is appreciated.

It's called Pot metal because you can Melt Pot, or was it it will melt before the pot does.

[Dynamo]

pot metal being a mix of aluminum and zinc, has a much lower melting point than aluminum alone. it is this reason why pot metal is used so much in airsoft, it's easy and cheaper to cast than aluminum. the problem though is that this alloy is much more brittle than aluminum, and should be avoided for use in any parts that receive repeated shock.

i believe the melting point is little more than lead 700°F to 900°F

[Drake]

The engine-enamel sounds like a bit of overkill given there's no heat being generated by the gun.

Why not a flat black epoxy enamel instead? (takes much longer to cure, but at room temp).

[The Chad]

Pot metal is a mixture of everything and anything to my knowledge, lead being the worst ingredient. If that's the case, heating it doesn't matter, bringing it back down from critical temperature is the issue. If you don't want to fuck with the grain structure, keep your shit below critical temperature for lead to be safe (621 F).



Edit: so pot metal used to contain lead. My mistake.

Keep it below critical temperature of the lowest melting point, I would keep it below 785F which is the melting point for zinc. If you really wanna know what it's made of, grind it.

[ILLusion]

As said, unless you know the exact elemental make up of the pot metal, you can't just guess at the melting point. But for what it's worth, I've had some pistol frames melt on me at less than 400°F during a powder coating process.

[Strelok]

Thanks for the help everyone. The can says to cure at 350 for about 40 minutes to an hour. So I should be in a safe zone at the least. Just worried due to the specificness of RPK parts and I don't like the idea of having to hunt them down.

Drake,

I'm wanting to use engine enamel due to the durability of it, that and I have pretty much unlimited access to it due to where I work.

However, what does the epoxy enamel have over the engine enamel? Aren't they essentially the same thing? Is Epoxy stronger? I'm just looking to add a very solid finish to the gun as the current is pretty flaky.

Thanks!

Edit: Wow, Illusion. That's pretty crazy, haha. Giving me second thoughts...

[ILLusion]

See my reply above yours.

Your best bet, is to take a sample of the exact same item you're attempting to bake and willing to sacrifice. Bake it. Note what happens.

[The Chad]

Technically if you control the cooling, you're good right up to critical.

[HKGhost]

If you're concern that it might deform at 350F for 40 minutes, bake it at 200-250F for 1.5 hours instead. Baking paint just cures it and does nothing else. So just go longer at a lower temperature to be safe.