C3 Heater Hose Brackets On Fender Well & Heater Box

[Richard F.]

I need some feedback concerning the finish on the C3 heater hose brackets (fender well & heater box), if you have first hand knowledge of the original finish on these brackets please advise.

My original 1974 brackets are not black, photo attached, any idea of what this finish is?

Thank You
Rich F.

[Russ S.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

I would suggest gray phosphate.

[Richard F.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Russ/Patrick

I would agree it's probably some type of phosphate as it has a dull finish.

Thank you
Rich F.

[Ron G.]

[Richard F.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Hi Ron

That is a possibility I have a N.O.S. one that I found in my 1974 engine compartment, I think I might have installed it in the 1970 LT1 maybe I can retrieve it before Sat.

And of course I'm just discussing the 1974 brackets, I wouldn't be surprised if they were bare metal (notice the rust on mine) or different phosphates over the years, I won't be conclusive until I find my N.O.S.

Thanks

Rich

[Ron G.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

I also have a new old stock bracket probably one or two of them and they are definitely natural but dull.

[Richard F.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Thanks Ron

Very helpful as N.O.S. or original could be the gold standard for proofing this stuff, the 1970-72 JM states black phosphate.

Rich

[Patrick H.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

I looked at photos of my late 72, and they look just like the ones posted here.
I also looked at other known natural (unplated) items in my engine compartment, and they all have rust on them. The appearance is quite different.

So, I lean toward zinc (gray) phosphate, not natural or black phosphate.

[Joe L.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

The original clips on my 1969 were phosphate-finished. I do not recall if it is what could be described as gray phosphate or black phosphate. My recollection, though, is that it was what could be described as a dark gray phosphate.

Keep in mind that phosphate is not a "forever" kind of finish. It's just enough to ensure that components stay relatively rust free "for awhile".

Also, this clip dates back to the later 50's and was used across multiple GM vehicle platforms for many years. So, there may have been multiple suppliers and those suppliers may have been able to apply multiple different finishes at their option.

[Terry M.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Phosphate is not usually intended as an appearance item. It is usually used to hold the lubricant during metal forming. It roughens the metal surface so the lubricant will adhere to the metal during the forming process. One will often see the surface specifications described as "phosphate and oil."
I could go on at length about when I worked in a metal forming research laboratory and we phosphated various metals in order to determine how various lubricants effected different metal forming operations, but it would bore most of you beyond belief. The phosphating operation involved fiberglass tanks with lead steam pipes in them. We heated sulfuric acid as part of the process. My sinuses haven't been the same since. Fortunately, (or unfortunately depending on your point of view) my experiences were from 1964 to 1968 and most all the government letter organizations didn't exist yet.

[Joe L.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Phosphate is not usually intended as an appearance item. It is usually used to hold the lubricant during metal forming. It roughens the metal surface so the lubricant will adhere to the metal during the forming process. One will often see the surface specifications described as "phosphate and oil."
I could go on at length about when I worked in a metal forming research laboratory and we phosphated various metals in order to determine how various lubricants effected different metal forming operations, but it would bore most of you beyond belief. The phosphating operation involved fiberglass tanks with lead steam pipes in them. We heated sulfuric acid as part of the process. My sinuses haven't been the same since. Fortunately, (or unfortunately depending on your point of view) my experiences were from 1964 to 1968 and most all the government letter organizations didn't exist yet.

Terry------

I agree; phosphating of metal parts is usually not done for appearance reasons. While I have no doubt it is also used for the purposes you describe, it's also used to "retard" corrosion. Many automotive fasteners are phosphate finished and there's no way this finish was applied before forming of the fastener.

[Richard F.]

Re: C3 Heater Hose Brackets On Fender Well & Heater Box

Terry/Joe

Thank you for the education, my original 1974 bracket finish is consistent with phosphate finish as originally were dull and I sprayed them with WD40 over the years but they still have managed to have a decent amount of rust.

Rich F.