Acid Test for Zinc

[Pardini]

I've got a chance at a boat keel, or at least part of one. Haven't seen it yet, but the seller guesses half a ton and says he's been told it's pure lead. I rather doubt it's pure lead, my only concern is Zinc in the mix.

I've read about using muriatic acid to test for zinc. How reliable is this test? I've watched you tube of supposedly pure lead bubbling in acid, which makes me doubt how valid the test is. Seems like if there is mostly zinc in the test alloy, the test would be pretty reliable. What are the Practical limits of the test? Has anyone done the acid test then backed up the results with XRF?

[bangerjim]

PURE lead will NOT react to acids.

HCl will cause an immediate and violent bubbling reaction to Zn. The lower the Zn content, the slower and lower the reaction.

H2SO4 will react much slower but will also bubble with the reation of Zn.

banger

[jsizemore]

No need to do the acid test if the XRF is available. I've done the acid test a bunch. I've had results that showed a little to pure. I made up some small amounts from COWW of zinc and lead alloy to see what the results would be for myself. I scrape the surface to test and use 10% HCl muriatic acid to test.

[Pardini]

I picked up some 30% HCl. Think I might be able to test a keel sample tomorrow.

Pure zinc was a pretty rapid reaction. Also tested several lead ingots from my stockpile and no reaction at all except to the surface oxidation of some that may be 20 years old or so. Scraped off the oxidized surface to bare metal and got no reaction on the same ingot.

Whats the lowest % of zinc the acid will react to when alloyed in lead?

[oley55]

pretty off topic but I can not get my head around the idea of anyone in the boat building industry intentionally including zinc in a boat keel. especially since sacrificial anodes are predominantly zinc. I have this picture of a sailboat keel with paint scraped off against sand/coral becoming hugely pitted like the anodes bolted to an outboard. I'm sure the mix is so diluted that excessive corrosion is not a real issue, but is does seem counter intuitive.

[bangerjim]

I picked up some 30% HCl. Think I might be able to test a keel sample tomorrow.

Pure zinc was a pretty rapid reaction. Also tested several lead ingots from my stockpile and no reaction at all except to the surface oxidation of some that may be 20 years old or so. Scraped off the oxidized surface to bare metal and got no reaction on the same ingot.

Whats the lowest % of zinc the acid will react to when alloyed in lead?

A few % will show up.....VERY slightly. You will almost need a microscope to see the reaction, but little bubbles will form over time. Anything less than 5% Zn, don't worry about it! Sure your boolits will be slightly lighter and you will have to add a bit more Sn to lower the surface tension, but no big whoop. I have ran test and found a few % is not big deal.

banger

[Pardini]

I did some more testing on my stockpile, this time using 20X. Looks like most of what I have has some small amount of zinc in it. Very slight bubbling that is only seen with magnification. Shouldn't be surprised, 98% has come from the bullet trap at an indoor range which lots of casters shot at.

The keel on the other hand, appears to be zinc free. So once the seller gets his cutting torch reg fixed, he'll burn it into manageable pieces. His problem, not mine and I've explained in detail why he shouldn't.