Re: T3 plating

[Chazpix@aol.com]

<Maybe Chuck  can explain why the button plating system is different from the
handle one.  Presumably something to do with wear characteristics?>

OK Dave here goes! Yes your absolutely right.
Everyone is familiar with the periodic table of the elements? Cool.OK, just 
as there are different hardnesses(lead is really soft-and diamonds are really 
hard) in the elements, metals have their own special characteristics too.
There are "base" metals and "noble" metals.(this is Electrochemistry)
Each have their own "potentials" or "activity".
These are classified in a "series".
This series is categorized into an "Electromotive Force Series".(measured 
from low to high)(also referred to as reactivity index)
The differences in thicknesses and type (of the plating) relate to the 
Electromotive Force Series(EMF) of the base metal(s) interacting(bonding) 
with the metal being applied (plated) ((noble metals on base metals or 
vise-versa)).Certain metals can be plated on certain metals, others 
can't,etc.(different reactions happen in & out of the tanks).  
Hope that makes a little sense!
Now, our door handles are made of zinc alloys(Zn) not steel (except the 
guts-they're steel).
These alloys have a different EMF than Fe (iron) ((steel)) and have to be 
treated differently during the plating process(& thought as to it's 
application afterwards).
(Zn castings need a cyanide solution because an acid solution will dissolve 
them)
Now here's an interesting test-take any magnet and try to stick it to your 
door handle button.(this is for early handles-but I think later are the same)
It won't stick to it! (high Zn content)((non-magnetic))
Now go to the body of the handle. It sticks a little.(about 50/50% Zn/Fe) But 
take the magnet & stick it to a door panel,or fender,etc.(watch your paint!) 
It sticks a lot.( high in Fe(iron) content)
This will give you an idea of the varied concentrations of Fe (iron) in the 
Zn  castings.(there are undoubtedly other metals for strength,etc.also 
combined in the smelting process)(our taillight housings are a "mix" also).
Depending on the EMF hardness/composition/intended use of the castings, the 
plating routines differ either a little or a whole lot (I.E. 
thicknesses/preparation/bath chemistry) (our buttons are plated differently 
because of the characteristics of their application-check out the average of 
Nickel on them(Ni is low reactivity,high hardness-almost neutral EMF) 
compared to both the handle body & even the overriders! (ever notice that a 
handle can look like cr@p but the button still looks good in a boneyard!) It 
has a higher corrosion resistance and higher physical hardness due to the 
increased thickness of the Ni.(but also notice just a "strike"or thin layer 
of Cu underneath-heavy copper will not adhere well to Zn) The handles have 
more Cu for protection(weathering) (remember the reactivity of the Zn, but 
also that the handle is a 50/50 mix-it will accept a heavy copper plate with 
the addition of the iron) but hardness isn't an issue for the plating there 
(hence average Ni content) what is needed is that the casting is 
stronger(more Fe) (also more magnetized).
Needless to say we hated plating alloys! Unfortunately car manufacturers made 
a BUNCH of these types of parts and if they're even a few years old they 
almost always need restoring.
Sorry for the lengthy post all!
Chuck Salter
'66 SB

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