Lead

[Ron Nossaman]

>Hmmmmmm? Having worked with most of the lead alloys, in my bullet/ball 
>making hobby, I'd say we're both right. And we're both wrong.
>The stuff that gets really swollen, etc., when melted/cast seems to be 
>soft. This stuff is very good for the bullets in a black powder rifle. (I 
>suspect it may have a small amount of tin. The pure lead, that I've 
>melted, for use in balls for my Black Powder Pistol, is softer than the 
>stuff above. It deforms more when loaded, which makes for a better seal in 
>the cylinder. Wheel Weight lead, on the other hand, is only suitable for 
>modern weaponry, as it holds it's shape better, in the reloading dies, 
>etc., and in target shooting.
>In conclusion, I suspect that the nasty stuff has small amount of tin. 
>Because of this, you have two disimilar metals that will interact and 
>cause electrolysis, which really what is happening here. Wheel weight 
>lead, on the other hand, has so much tin in it, that is resists 
>electrolysis/corrosion, IMO. As all of this is speculation, on my part, 
>gained by melting the various types and using as bullets/balls. K?
>Best Regards,
>Joe Garrett, R.P.T.

Lead and tin are right next to each other in the electromotive series 
chart. That means they are very compatible, and will mix gracefully without 
producing a corrosion cell. The addition of tin doesn't make lead less 
susceptible to corrosion, it just doesn't cause it. Regular old 50/50 
solder is half lead, half tin, and isn't remotely prone to corrosion. The 
farther apart two materials are on the chart, in contact, in the presence 
of an electrolyte, the more active the corrosion reaction, and the material 
higher in the chart will be the anode, and will actively corrode. So 
whatever contaminant is in the old key leads that made for the dramatic 
exfoliation corrosion, it ain't tin.

Ron N