smog tubes plating
 

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

Re: smog tubes plating
 

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

Re: smog tubes plating
 

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.

Re: smog tubes plating
 

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.

Re: smog tubes plating
 

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

Re: smog tubes plating
 

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.

Re: smog tubes plating
 

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

Re: smog tubes plating
 

rick, that looks like a brown green color?

Re: smog tubes plating
 

Yes

Re: smog tubes plating
 

which would be the olive drab finish I believe?

Re: smog tubes plating
 

I would not call it Olive Drab by any stretch as that is a much more flat green color than these were but they definitely have a green tint to them.

Re: smog tubes plating
 

Rick,
Are you sure those were NOS? I question that because of the amount of steps in the transition from main body to the outer branches of the tube. Originals I have and have seen use 2 steps in downsizing the main body to the outer branches whereas repops commonly have 3 like what yours look like. My NOS ones are also more of the brown-black finish that I've had on survivor originals with the 2 steps. I'm sure the color varied in production, but I've not seen anything as green as yours look from GM from the the 69-70 time frame.

Re: smog tubes plating
 

Well lets just say that they both came out of original GM boxes with the correct part numbers but we all know how that can work today.....maybe I got duped....again!

Re: smog tubes plating
 

The pic in post 543326 looks like the tube is parkerized with oil on it. I have had bolts plated this way and washers that can look like this tube.