Hi Rudy! First, I don't have an exalted position - I'm just a grunt working in
production! What is your definition of corrosion? Oxidation is can be
classified as corrosion depending on the metal (e.g. iron) but oxidation of tin
or tin/lead is not corrosion. There is a number of sources of EMF tables that
are more than just deionized water based - they work quite well in a number of
industrial applications to predict potential galvanic issues. Solder does have
better corrosion resistance than pure tin but to suggest that there is a
"profound" difference implies that the hundreds of tin plated aluminum
electronics housing in the field are undergoing corrosion problems which is just
not true. I guess we'll agree to disagree on this issue.
Dave Hillman
Rockwell Collins
[log in to unmask]
[log in to unmask] on 11/05/99 08:49:42 AM
To: [log in to unmask], David D Hillman/CedarRapids/Collins/Rockwell@Rockwell
cc:
Subject: Tin vs. Tin/Lead solder
Dave:
With all due respect to your exalted position in this area....
I have seen many many problems in the fabrications area caused by having pure
Tin, as compared to having Solder, especially if the it is true solder, i.e.
that it is the true alloy, which seems to have profoundly better corrosion
resistance than merely "plated solder", which is nothing other than discrete
chrystals of Tin and Lead.
(Should I note that we make money and have products which have a life only
because they solve this issue... in selected situations:-)
And ignoring any ostensibly authoritative EMF tables, which I have found to
be effective in academia, and few other places (because they are meaningful
only when the electrolyte is deionized water), the solder seems to have much
better resistance to corrosion than pure Tin, and especially plated Tin,
which seems especially "active".
If what I am saying is true, that Solder is much more passive than pure Tin,
you have the makings for a seriously pumping galvanic cell, which should need
only an electrolyte to crank up, and deliver you Tin oxide all over the pure
Tin plating...
And remember, free advice is often worth what you pay for it...
Regards,
Rudy Sedlak
RD Chemical Company
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