How do you know that any of these salvage pieces are Zamak,
In short, other than reasonable guesses, I don't.
Rather than another random pot metal alloy of similar density?
Similar density and melting point? Zamak is heavy and melts on a stove. Not much else will do that.
I took samples of each and put them on a burner first to make sure they melt in isolation, not dissolve into the alloy (which can happen at a much lower temperature).
I was using mostly mass-produced cast items, not oddball junk, which gives me higher hope.
- Conduit fittings are pretty reliably Zamak. Fire hazard and industrial corrosion, I can't see them just being pot metal. They all came out of commercial facilities.
- The 2-hole punches are old, Canadian-made, and heavy duty
- The CVT pulley was US made.
Those were 98% of the mass of the melt, I'm reasonably confident they were proper Zamak die cast. More importantly, because they're all old already, I'm reasonably sure they don't have lead-inclusion leading eventually to "zinc pest" where the lead crumbles the zinc away because there no signs of that, and even then, that takes decades after a new melt. I might be dead before that happens.
The towel holders and knobs I'm less confident of other than their melting points. Probably should have excluded them since I was clearly over the minimum I needed and they might have had lead or cadmium or who knows what dissolved in them. Almost certainly chinese made, and cheap/thin. They went in last and because of the chrome plating, ended up being mostly dross that was removed anyway.
Also, economics. There's shortcuts to take in terms of not properly sorting scrap metal, but anything else thrown in deliberately is going to be more expensive than zinc.
Tin and Zinc weigh almost exactly the same, but tin is 8x the price so there's not point in using it. Lead is about 2x the price.
Nothing else would melt at that low of a temperature. Aluminum and copper would dissolve into the alloy I suppose, but again, each are more valuable on their own.
How do you know which Zamak alloy they are, or that they're the same as each other?
I don't, but it doesn't matter, they're all in the same ballpark and the alloy differences aren't magic. The more X you put in, the more you start to see properties associated with that alloy. If they're many different alloys, I'll have an averaged out performance of whatever was in the pot. I probably should have sprinkled in some more copper, tends to make it stronger, but, then I'm having to stir it to make sure it dissolves equally and then I have more dross and air dissolved so, meh.
For example, wiki says: "Zamak 5 has the same composition as zamak 3 with the addition of 1% copper in order to increase strength (by approximately 10%[17]), hardness and corrosive resistance, but reduces ductility.[31] It also has less dimensional accuracy".
So, if I mix 50% Z5 with 50% Z3, I'm at worst losing out on 10% strength gain, but most likely just gain 5% strength and hardness instead of 10%. If I accidentally add 3% copper, I've made Z2 which has 20% more strength increase, but becomes brittle over time. Z4 has less copper than normal, and it's to prevent the melt from sticking to the dies. Z7 has more magnesium so that it's thinner and fills small voids easier.
... none of this matters. If I mix a bit of each, I'm getting partial changes in the properties. And I'm casting a giant slug of it, not picking up delicate surface features.
It's almost certainly all Z3 anyway. Basic boring industrial stuff.
Perhaps most importantly... DIY EVers have typically made couplers out of aluminum, which is weak and brittle compared to zinc. I'm building a zinc coupler of comparable size, so, minute differences just won't matter.
Or... I'm wrong, and it falls apart after use. I guess we'll see.
