Parking Brake Frame Guide Bar Finish?

[Hans L]

Does anyone know what the correct finish is for the Parking Brake Frame Guide Bar?   Mine had surface rust so I can really determine the original finish. 

Based on variety of searches, I’ve seen the following finishes -

-   Painted black
-   Natural steal
-   Phospated
-   Or?

I’m leaning towards phosphate, but not sure.

Reference Parking Brake Frame Guide - Cleaned/Surface Rust Removed:

[Mike S]

 Below is a picture from my 67 05B NOR.
After cleaning it with Evaporust, there remained several small spots that look like areas of dull zinc plating (pointed by arrows).
 
Mike

[firstgenaddict]

It may have been BLACK ZINC.
Which is a black passivation of ZINC.

[68camaroz28]

It may have been BLACK ZINC.
Which is a black passivation of ZINC.

Interesting Mike & James! When we restored our 68 our rod had some very minor surface rust but overall a clean piece and after sitting in evaporust for awhile I thought it seemed to be a phosphate color and since it came out so new looking out of the evaporust bath it was protected and put back in the car during restoration. 

[Mike S]

 The equalizer also had what looked like zinc remains. So, when I placed it in a mild acid solution to clean it before plating, it fizzed quite a lot, so that tells me there was definitely plating on the piece to react with the acid.

Mike

[Edgemontvillage]

The equalizer also had what looked like zinc remains. So, when I placed it in a mild acid solution to clean it before plating, it fizzed quite a lot, so that tells me there was definitely plating on the piece to react with the acid.

Mike

Mike, I too thought it was either silver cad or clear zinc plated based on what came off my car. I re-plated
maybe mine silver cad however would like to develop more confidence in that choice. So far we’re heard almost the full gambit!

[firstgenaddict]

The problem with determining whether the ZINC was passivated black or olive is that PASSIVATION is by definition forced oxidation. Therefore the problem with using things such as evaporust or Vinegar or Citric Acid is that they remove oxidation therefore they will remove passivation.

I learned the hard way and did some research as I have a 1973 ITM shifter which has OLIVE PASSIVATION of the ZINC. (olive is the hardest ZINC passivation) 
When I dunked it into evaporust it came out PERFECT BRIGHT ZINC. --- now I have to re-passivate it with Olive.

FWIW pretty sure the olive fuel line clips are zinc plated then Olive passivated.



 

[Edgemontvillage]

James, an informative and interesting explanation (and hypothesis). What’s involved with doing Olive Passivation? I assume the trunk lock retainer bracket was also Olive Passivated?

[169INDY]

The process of chromate conversion coating of zinc plated parts is *sometimes* called "passivation".
Conversion Coating – A coating produced by chemical treatment of a metallic surface, for example, chromate conversion coatings on zinc, cadmium, copper and aluminum; black oxide coating on steel. These coatings are intended to provide some corrosion protection, or a better surface finish for additional coatings which provide the majority of the corrosion protection.

ASTM-B633  Type II  - with colored (di)chromate conversion coating(with supplementary (di)chromate treatment), The chromate conversion coatings are available (usually) in blue, yellow, olive drab, black etc

I will ask our Plating plant Electroplater Plannerman what is used to achieve the olive dye coloring

Commercial item located here (Please note they do not call it passivation)
https://www.caswellplating.com/electroplating-anodizing/zinc-plating-kits/chromates/olive-drab-green-chromate-makes-2-gal.html


Jim

[Mike S]

This picture of the 67 LOS trunk plate appears to be gray phosphate, no green at all. This is the same for my NOR too.

Mike

[Camarocards]

Like Chick, I too, put mine in Evaporust. Came out very clean so I just put some surface protection on it to prevent future rust. FWIW, attached are a few photo's.

Bob

[Mike S]

I wonder if in 67 they were plated and then not in later years to save a few cents per bar.

Mike

[Hans L]

Interesting responses - appreciate it!   For the Parking Brake Equalizer and Connectors, I assumed/concluded clear zinc/silver cad based on observations of the pieces, but not 100% sure as I've seen some Equalizers painted black.  For the Parking Brake Frame Guide - I wasn't able to discern much, but leaning still sorta leaning towards natural steel finish.  I think we can conclude painted black is probably out.   

Regarding the Olive finish - other than clips, the only other component I can think of are the smog tubes.  What is the benefit of the Olive Passivation and why would GM apply that finish to the Parking Brake Frame Guide?  Does it offer additional protection properties?

[hrlyfxdl]

Just to add to the conversation, here's one I recently bought on ebay for my car. It looks just like the picture, and the finish. Thanks

[Mike S]

Are the shiny spots clean metal or the remains of plating?