70 Corvette dust shield plating

[Lynn]

Back when I restored my 69 Z, I (like most folks at the time) had them plated silver cad.

They came out very nice, and are still looking good today.

Then I read a thread on here that they SHOULD have in fact been galvanized.

Tearing down the 70 Corvette LT-1 chassis. Dust shields look about the same as the ones on my Z before plating. Dull silver color.

Question: what is the correct plating?

[LT1vette]

Where are these shields located?

[napa68]

This is from my 8900 mile car......

[Lynn]

Thanks. I have three that look almost that good. Any idea how it is plated?
Silver cad? Galvanized? Painted?

This car is not getting judged, and will have a couple of day two parts. But, I still want it somewhat correct for when I go to sell it.

[MosportGreen66]

Mike Gibbons just did the dust shields on our '70 L78 Nova. Great work and site sponsor.

[70post]

Maybe there was some variation on the plating used on these front disc rotor shields.....I have originals from 2 '70 Oldsmobile Abody cars and they are absolutely galvanized. Same thing for a '72 Buick Stage 1 car.

I think the only option these days is to have them clear (silver) zinc or cad plated. Repros are zinc plated as well. I've seen where people take things like crumpled up foil or cellophane rubbed in a silver paint and then "dabbed" on the surfaces to try and emulate the galvanized look.

The shield in posting #3 above doesn't have that distinct galvanized "pattern".......maybe it's just the photo and I can't see it, etc or then again, maybe that one isn't galvanized.

And yes, Mike does very nice work!

[RPOLS3]

I think the only option these days is to have them clear (silver) zinc or cad plated. Repros are zinc plated as well. I've seen where people take things like crumpled up foil or cellophane rubbed in a silver paint and then "dabbed" on the surfaces to try and emulate the galvanized look.



Galvanizers are becoming tougher to find for sure but I was able to get my originals re-done through an ornamental iron supplier I work with.

[Too Many Projects]

VERY nice !!
Looks like you could set up a nice sideline with that plater...:wink:

[SS427]

Jake, those look fairly accurate. I have yet to find someone who could galvanize them correctly and yours are damn close albeit a little shinny. I did these using the mottling process 70post mentioned earlier. I think I got them fairly close.

The first photo is of a pair of NOS. The second photo is mine on top of the NOS and the last photo is mine overall.

I have also had mine zinc plated and then hit them ever so lightly in the glass media cabinet to dull them a bit. Those looked pretty good as well.

[Lynn]

There are two galvanizing processes. One is hot dipped, and gives the mottled look. I doubt GM hot dipped them, just because of the added expense. Seriously, they were not anticipating us scrutinizing these finishes 50+ years later; and frankly didn't give a rat's a$$ whether they would last that long.

The other process is electroplating. Much cheaper. The finish looks more like silver paint. The downside is that they do not last nearly as long in a harsh environment. My brother chewed me out for bringing home some electroplate galvanized roofing nails. I had no idea.

Now I am wondering if GM used electroplate galvanizing. That would explain the pic in post #3 NOT having the distinctive pattern. I can assure you that the "virgin" (albeit a 54 year old virgin) shields that I have do NOT appear to have been hot dipped.

I will post pics when I get them off.

I cannot express how much I appreciate the pros, as well as the other very knowledgeable folks who post on topics like this.

[70post]

I don't think GM did any of it....meaning my bet is that the roll steel sourced for the dust shields was specified to be galvanized (at the mill,etc). Then the pieces got stamped out from the rolled sheet steel.

Galvanizing served a sort of dual purpose...protected the metal pieces that were stamped out from the rolled sheet AND lessened the wear and tear on the stamping tooling (since zinc is a soft metal). Same thing on alternator fan blades and many other parts.

Just my "speculation" on this.....gas tanks are the same thing/process (albeit a different coating/plating)....at least when it comes to the GM Abody cars of the era.

I'll try to get a pic or two of one of the galvanized dust shields I referred to above.

[napa68]

Thanks. I have three that look almost that good. Any idea how it is plated?
Silver cad? Galvanized? Painted?

This car is not getting judged, and will have a couple of day two parts. But, I still want it somewhat correct for when I go to sell it.

I was of the opinion cad plated

[BCreekDave]

I don't think GM did any of it....meaning my bet is that the roll steel sourced for the dust shields was specified to be galvanized (at the mill,etc). Then the pieces got stamped out from the rolled sheet steel.

I'll try to get a pic or two of one of the galvanized dust shields I referred to above.

Seems to me that if the roll steel was galvanized and the stamping happened later, that the cut edges would be very prone to rusting. Most moderately used ones that I have seen do not show evidence of this.

[Lynn]

Have to agree with Dave on this one. I would THINK (not my best arena.... I quit getting lost in thought, as I feel like a total stranger there) that whatever plating was done, it was done after the part was formed. IF they are in fact galvanized, it certainly looks like electroplate galvanizing to me. After a few years, that plating would be virtually indistinguishable from silver cad to the naked eye.

Any chemists on here? Any test I can run on one of the bent up dust shields I have to determine finish? Three of the four extras are as nice as the ones on Tim's 8900 mile car. The fourth one; not so much.

[Dusk Blue Z]

Any thoughts about the raw steel being hot dipped and then the plates being stamped out like gas tanks were?

Mike

[Lynn]

I don't see a problem with it as long as there is no trimming needed after dipping.
In other words the blank is already the exact size needed for the finished item.

[169indy]

A great source of Data might be a GM drawing for the J52 or JL8

[Lynn]

These guys seem to think that they were cad plated.

https://www.ebay.com/itm/174286184364

Although they offer the same part for 68-82.

These guys believe silver cad plated from 65 through 1975, then gold cad plated from 76 through 82.

https://www.topflightautomotive.com/products/chevy/corvette/c3/brakes/brake-dust-shield/

[automotivecraft]

Hi Lynn, According to the NCRS judging guide (6th edition):
Original front-brake backing plates are dull cadmium or zinc plated, while the rear backing plates are punched from a sheet of galvanized metal. The sheared edges are bare steel and may exhibit some rust on the edges. Later service replacement backing plates are a zinc dichromate finish.
Fran

[Lynn]

Thanks.

[Lynn]

Ordered the judging manual from NCRS. Figured I would save a lot of time asking questions and can get back to work on the car.

Although, one more question. Was cleaning up one of the front dust shields (definitely not hot dip galvanized) and there is no part number. It looks just like the one Tim posted in post #3. Am I right in assuming that, just like the exhaust tips, the assembly line parts have no part number stamped on, but the over the counter replacement ones DO have a stamped part number?

BTW, I looked at the rears. Will be a while before i disassemble and get to them, but there does not look to be any bare metal on the edge.

[CamarosRus]

Top Two pics are 2nd Gen Camaro NOS 2nd design with Rolled Edge (not Sharp)
Bottom Two pics are 70 Camaro Survivor ..........

I have always thought these were stamped form Galvanized Sheet....but wont argue
with Dave about non rusting edge............

[Lynn]

Chuck. Gotta keep in mind that NOS isn't always the same as assembly line. Things changed over the years.

In the early 70s I purchased a brand new hi-rise for a 69 Z/28 from the local Chevy dealer. Instead of a 472 intake, I got a 2116 intake. They look identical.

[Lynn]

Would vapor blasting clean my originals but leave the plating intact?

If not, how about dry ice blasting?

[dl7265]

Would vapor blasting clean my originals but leave the plating intact?

If not, how about dry ice blasting?

Depends on the media in the Vapor hone. I use a fairly fine glass. ( won't remove rust ect)

Take a Look at Level 1 dry ice blasting. That won't remove any material. And will leave plating intact. ( one of the best benefits imo )

[napa68]

Lynn,

Got any pics of your backing plates? I cleaned the plates from my 67 L79 with nothing more than the parts washer and Boshield. I still maintain they are cad plated.

Tim

[Lynn]

13 degrees f here today. My shop is heated, but giant wuss that I am, I don't know that I want to go outside long enough to go down and turn on the heater.

I cleaned one in the solvent tank. Still has some residue on it. Tim, my guess is you are a much more patient man than I am.

Will try to get pics sometime soon.

[68camaroz28]

Depends on the media in the Vapor hone. I use a fairly fine glass. ( won't remove rust ect)

Take a Look at Level 1 dry ice blasting. That won't remove any material. And will leave plating intact. ( one of the best benefits imo )

Walnut sheals ? (never tried for that application) JohnZ mentioned many years ago RIP, which I've used quite a lot is glass beading at a low 25PSI which works well when trying to keep the same texture/look.

[CamarosRus]

I use my CERAMIC Media Shaker/Tumbler Machine to CLEAN the Galvanized Surface.....as well as my Aluminum Die cast parts, Tie Rod Ends and many other parts

[Lynn]

Here are pics of the RF dust shield.
Sadly, the LF is not usable. But, I have a spare. Just haven't tried cleaning it up yet.
I may be searching for a survivor LF.
Glad to have two pristine rears.

Frankly, I cannot tell just by looking whether these are cad plated or galvanized. I am certain they are not hot dipped galvanized. That process leaves a very distinct pattern. Just LOOKING at them without any kind of chemical analysis, they COULD be electroplated galvanized. Hard to tell on a 54 year old part!!!

Roy S told me:
"Front: dull cadmium without dichromate conversion coating. These tend to get chalky look to them with aging.
Rear: punched from galvanized metal sheet, sheared edges are bare steel from the shearing action which could and did rust."

I let this one soak in solvent (Crown PSC1000) for about a week; then scrubbed on it with a soft scotch pad. As you can see, there is still some discoloration on it. I didn't want to scrub hard enough, even with a fairly mile abrasive, to disturb the original finish.

[napa68]

That looks nice Lynn!