finish for these underbody plates

[Michael L.]

Guys,

I'm re-finishing the underbody plates on my 69 coupe. The JG states that Seat belt anchor plates are Cad plated, the front seat anchor plate is chassis black, and the rear seat anchor plate is black phos. My problem is, I'm not sure which plates the JG is referring to. There are a number of plates under there and I can't tell which they are referring to. I've attached a few photos of the underbody and have labeled some of the plates with tape for a reference point. In the first photo I'm thinking the plate with the tape is the rear seat belt anchor and it should be black phos. It wraps around the side of the main underbody support. In the second photo the plate with the tape is the seat belt anchor and should be Cad, and the plates in the rear wheel well area I've already painted Cad finish because I thought it was a seat belt anchor point but is this correct? Are the small rectangular plates next to what I believe to be the rear seat plate and the seat belt anchor supposed to be chassis black? Any assistance is appreciated.

Mike

[Michael L.]

Re: finish for these underbody plates

Just wanted to recycle this to the top to see if anyone can help me out on this. Thanks for any assistance you can give.

Mike

[Gene M.]

Re: finish for these underbody plates

Rear seat thick gauge anchor plates are natural steel. I do not agree with manual on these. Front seat anchor plate is black paint. The inner and outer seat belt anchors are plated, some times look zinc and other times galvanel or phosphate. The tire well shoulder seat belt anchor is painted over black during black out. These parts are differing in configuration from mid years but functionally the same. The retractor plates I’m not sure, but my best guess would be phosphate.

[Michael L.]

Re: finish for these underbody plates

Thanks Gene. After reading your post and doing some research I've come to the following (tentative) conclusions:

1) The plate in the lower half of the first picture without any tape on it with the large square nut on it is the outer seat belt anchor plate, and the plate in the second picture with the tape on it labeled cad is the inner seat belt anchor plate and they are both cad plated. Correct?

2) The rectangular plates with the cut off corners (four of them for the four rear seat anchor points) are the rear sear anchor plates are either natural or black phos. Correct?

3) The triangular looking plate in the first photo that wraps around the side of the main underbody support and is labeled in my pic with yellow tape and Blk phos on it (although it is hard to read) is the outer seat belt guide reinforcement (as opposed to seat belt anchor) and is therefore painted chassis black. I believe you referred to these as retractor plates in your post and you guessed that they were phos plated. Did you mean black phos, or something else?

Thanks for any help you can give.

Mike

[Gene M.]

Re: finish for these underbody plates

Mike,
Cad plate by 68 and forward was not a finish in favor at GM and most other factories. You will find zinc is the finish most sought after by GM another is galvanel a preplated material to cut costs.

Phosphate is any where from gray to black in color. Functionally the same and often both seen on mechanical parts. It is a heated dip process.

For the function of each part it is a simple look at the position they are used in seen from interior of the car.

[Gary B.]

Re: finish for these underbody plates

I have a late 68 here. I would suspect they are very similar to you 69.

Front seat mounting sheet metal plate is dip-painted semi-gloss black.



The rear seat mounting plates are a dark gray phosphate.

[Michael L.]

Re: finish for these underbody plates

Thanks guys. Very helpful.

Mike

[Gary B.]

Re: finish for these underbody plates

The rear seat belt anchor plate looks to me either faded zinc or cadmium. Definitely not a phosphate finish.





The triangular piece you currently have black, on this car is definitely a bright plating, my guess a zinc-plating.

[Michael L.]

Re: finish for these underbody plates

Thanks Gary. That's super helpful. since the JG does not differentiate between how these plates are finished in 68 vs 69 I will assume this finish carried over and will go with what your pics show here.

Mike