The Official 356Talk Forum

Cad I plating is a "thing of the past" w/having national regulations as a safety situation "unless it's done underground". Zinc is too bright and difficult to finish evenly;
I have good looking covers w/Dull Aluminum by Krylon and just before it dries, I spray w/clear lacquer for final cure. Yes, the retainer spring will scuff the surface during
R & R, but it's the same w/the front & rear latches which passes inspection that shows the servicing of engine, filling the tank, etc. is/has been done; Never touched up.
To minimize 'scuffing', I use a piece of thin plastic (or tape) and a wood dowel to pry under the retaining spring to lessen the pressure when snapping it into place.

Modern-ish zinc plating uses an acidic bath of zinc salts and a chromate finish over the top to give it the bright, clear (with blue tint) shine. This is not what was used in the 1950s and early 1960s. Instead, an alkaline cyanide bath was used to deposit the zinc, which gave a much more matte finish. It's likely Porsche's suppliers in this period used this or a similar method. The result was a frosty finish.

If you need to replate using zinc and want an authentic finish, then make sure your plater knows that it should be a more matte finish. Frosty, not shiny. This probably means foregoing brightening agents or changing the chemistry of the baths.

Clearly cadmium is bad and should not be used.

Tom, I am very interested in fastener types and finishes and also have an early 56 coupe that I am constantly refining. Would you be willig and able to share the information you have?

I disagree with the statement that the original type of zinc plating was more dull than what you get today. It was actually pretty bright. Those we have had good condition original pieces in their hand can attest to this. Especially bolts which got touched up with paint by the factory will yield a good idea on what the plating looked like when stripped.

I do agree that the blue chromate offered today will not make the pieces look original. I have been having pretty good luck with my plater recently as they were forced (by the environmental people) to change the formulas. The stuff I get back now is more more silver and lacks the blue hue. Still not quite the same as original but beggars cant be choosers

Note the brightness of the upper half of the fuel pump.

Thanks Tom, also notice the high sheen on the valve covers