Lemme butt in with some theoretical stuff, that I have seen evidence of.

The subject is galvanic corrosion, or what happens when you have two metals
(like Tin and Lead) electrically in contact with each other, and with the
corrosive material.

When this is the case, the more readily attacked of the two metals (in this
case Tin) is MUCH more readily attacked, while the less readily attacked
metal is protected.  This is why galvanized pails do not rust as easily as a
bare steel pail would, that is why you "galvanize."

However, in this case, you are trying to protect the entire exposed surface,
both Tin and Lead, and keep the surface solderable.  So, this is not such a
good idea, as the presence of the Lead should/would accelerate attack on the
Tin.  Or, what I am suggesting is that by this theory, Tin/Lead should be
LESS protective than pure Tin.

(All of the above advice goes out the window if you fuse or "reflow" the
Tin/Lead deposit, in which case the plated metals form a true alloy, instead
of discrete crystals of Tin and crystals of Lead, and thus act like a single
metal.)

Remember, free advice is often not worth what you paid for it....:-)

Rudy Sedlak
RD Chemical Company

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