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[T3] T3 Tach conversion/plating


Thanks Per. I'll contact him and see if he's got pictures/find out how much.
 On chrome plating guys and gals...Actually the condition of the parts can 
range quite a bit. No matter how much dirt & grease are on the parts they 
still have to be stripped in a hot caustic soda(sodium hydroxide) bath to 
remove all traces of paint,dirt,grease,silicone sealer,etc.(basically 
anything on the base metal) Then it's rinsed & placed in a HCl (hydrochloric 
or muriatic) acid bath (pickling) to remove all traces of rust (for steel 
parts). Here is when you find the true condition.(just light corrosion or 
heavy pitting or holes all the way through the metal).
Then begins the real work. If there are holes,they can be welded,brazed,or 
soldered,then ground smooth.(flush to the surrounding area) Back to the 
stripping tanks to remove flux,soldering paste,etc.(both NaOH & HCl)
Now into the plating room for a heavy copper plate(this is the most important 
part of the process) Think of copper as the "primer" in painting. Since it is 
a soft metal, it is "flowed" rather easily,(trade jargon) that is to say 
worked smooth with a combination of Greasewheel/Sisal polishing wheels (looks 
like fine sandpaper/ broom bristles on a wheel) the combination of these and 
other buffs & compounds "flow" the copper into pits/scratches/other 
imperfections in the bare steel & make the surface very smooth.
Now the part is sent back to the stripping tanks once again.(to remove 
polishing greases/compounds) 
Back to the copper tanks(this is the point at which the corrosion protection 
is maximized.(or the length of time the plating will last) The heavier the 
copper plate here,the more"protection" the steel has.(remember copper does 
not rust)It's buffed with a softer compound (tripoli) and softer buffing 
wheels(cotton sewn/coloring)
At this point the piece will be very highly polished.(mirror reflectivity) 
Again to the stripping tanks.(remove tripoli/fingerprint oils/microscopically 
clean)
Again to the copper tank for a quick "strike" (in & out of the tank w/another 
very thin film-for adherence) rinsed twice,and straight into a nickel plating 
bath(here again,more is more expensive,but protection and lustre is 
dramatically increased).Rinsed.
Now finally it goes into the chromium plating bath, where for the most part 
is in there for a very short time.(chrome is VERY thin compared to the other 
metals) Good electroplaters will position the anodes in the chromic acid tank 
to "throw" the plating into the little nooks and crannies of the 
part.(although so much can only be done with this-you may have noticed some 
areas look "yellow"-these are the places where the Ni shows & Cr didn't throw)
This is known as a TRUE triple plating(Cu/Ni/Cr) Some shops will polish the 
bare steel,Cu strike it, Ni plate & then chrome plate-this will rust very 
quickly because there is no heavy copper plate under the nickel to protect 
the steel.(and you can tell because it does not look "that shiny"!)(most mass 
produced chrome parts are done this way)
Sorry for the long post all.(used to plate for a living & thought folks would 
like to know why the process is so expensive and time consuming,but when done 
right, plating should look beautiful and last a very long time! )
Cheers!
Chuck Salter
'66 SB
P.S. as to running hotter with chromed tin, we tested components with various 
coatings(powdercoat/paint/plating) and found no discernable difference in 
engine operating temperatures with plated parts.

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