smog tubes plating

[enio45]

I have seen some orig smog tubes for the 69Z and have noticed that the orig colors on them
have a greenish finish. When I have restored these before we used black zinc - but was wondering
what this green finish is and can it be duplicated/special plating?

thanks syc

[169indy]

excerpt from: ASTM-B633 ZINC plating;

http://www.techplate.com/zinc_cad.htm

Properties of the Chromate Finish
Even though zinc and cadmium are excellent rust retarders the surface of steel coated with these metals does not remain bright and stain-free in service. To avoid staining and delay the formation of white corrosion products during storage or in service indoors, practically all zinc and cadmium-coated steel manufactured today is given a thin (20 micrometres maximum) protective film using one of the available chromate conversion finishing processes. There are three classes of chromate finishes in general use on cadmium and zinc coatings: blue brite, clear (single dip or leached) iridescent yellow, black and olive drab. The thickness of the finish increases in the same order, the olive drab being relatively much thicker than the others. Which class of finish is selected depends upon the kind of service to be met and the properties desired in the finish.

I am not sure if you can post treat a black Zinc job with a additional chromate conversion coating to get the green tint. I could be possible.

Jim

[enio45]

wow, a lot of info in that link and quite useful.....I need to check to see if they can do small work like plating for the smog tubes in the olive drap.....ill report back what I find out...I also sent this to steve gregorie to see if his processes can provide this as well.

[camaromb]

I believe the original finish was black but poorly done in large production which resulted in the bronze tones that we see on original tubes.

[enio45]

mark, intersteing - I thought for sure the ones I have seen had the green tint to them....have u seen any nos tubes or mint orig that u can verify - before I decide which way to go redoing the exh tubes?


appreciate the help

[Steve Shauger]

I've observed a dark bronze finish on many original cars, although as Mark stated they were supposed to be black. It will be interesting to see what Steve Gregori's finish looks like. Below is an example of the brown finish on an original RH-BB smog tube.

[SS427]

Here is another photo of what the coloration should look like. These were NOS.

[enio45]

rick, that looks like a brown green color?

[SS427]

Yes

[enio45]

which would be the olive drab finish I believe?