Radiator cap restoration

[John D.]

Re: Radiator cap restoration

Noted.

I know that we had one anaylzed for our Restorer story a couple of years ago and it had been replated in cadmium. The cap had allegedly been restored by you - apparently that was incorrect.

Thanks for the information.

Patrick

Dr. Patrick, Sometimes zinc plating can closely resemble cadmium plating. Not all zinc plating comes up bluish. If you eliminate the final dip it comes out similar to cad-but fake looking. Trouble is that it is not as durable as cad plating. And it is not quite as soft looking as cad plating.
Not disputing the fact that you said you had someone anaylze the cap though. Just saying he may not have been aware of the various types of zinc plating. Down the road when cadmium is outlawed everywhere we may have to resort to the zinc plating without the blue. John D.

[Joe L.]

Re: Radiator cap restoration

Dr. Patrick, Sometimes zinc plating can closely resemble cadmium plating. Not all zinc plating comes up bluish. If you eliminate the final dip it comes out similar to cad-but fake looking. Trouble is that it is not as durable as cad plating. And it is not quite as soft looking as cad plating.
Not disputing the fact that you said you had someone anaylze the cap though. Just saying he may not have been aware of the various types of zinc plating. Down the road when cadmium is outlawed everywhere we may have to resort to the zinc plating without the blue. John D.

John-----


Once-upon-a-time when I was working and had access to our laboratory with atomic absorption spectrophotometer, I took scrapings from a variety of original C2 and C3 Corvette pieces often described as "cadmium" plated and analyzed them. I don't recall that a single one turned out to be cadmium rather than zinc. So much for that "myth".

It is possible that some or most C1-era stuff was cadmium plated. However, I don't think that very much C2/C3-era stuff was. Most GM specifications for parts called for EITHER cadmium or zinc. Under those circumstances, I don't know why any supplier or plater would have used cadmium unless they were set up for primarily cadmium plating. And, except for platers that did primarily mil-spec work, I don't know why any would have been set-up primarily for cadmium plating.

Is cadmium more durable than zinc? Yes, it is to a rather small degree. Would that durability difference ever be of value to us as Corvette restorers? Not unless we decide to use the cars under all-weather conditions AND we live to be a lot older than any of us are likely to live.

[Patrick H.]

[Patrick H.]

Re: Radiator cap restoration

As Joe notes, we had them analyzed with spectrometer. No guessing involved, at all.

Original were zinc plated.

I went back and looked at my notes. It's some of the REPRODUCTIONS that are done in cadmium (who would have thought?), not the Pirkle caps. Sorry again for my error on that one.

Patrick

[D S.]

Re: Radiator cap restoration

Patrick, thanks for the additional information which clears up an earlier comment here that, at the time, seemed contradictory to the 1970-192 Corvette JG, 4th Edition.
I found and re-read the excellent radiator cap article you and Tony Hurtado wrote in the Winter 2006 edition of the Restorer which cleared up questions I had about the differences between Design 2 and Design 3 caps. I sent Tony an email a few minutes ago requesting clarification on a couple of nuances.
I think for driving purposes I will purchase a functional reproduction RC-15 from Tom DeWitt and if I ever decide to enter my Corvette into the NCRS judging events I will have a real RC-15 cap in my pocket.
Thanks to all for your comments and recommendations.

[Patrick H.]

Re: Radiator cap restoration

Patrick, thanks for the additional information which clears up an earlier comment here that, at the time, seemed contradictory to the 1970-192 Corvette JG, 4th Edition.
I found and re-read the excellent radiator cap article you and Tony Hurtado wrote in the Winter 2006 edition of the Restorer which cleared up questions I had about the differences between Design 2 and Design 3 caps. I sent Tony an email a few minutes ago requesting clarification on a couple of nuances.
I think for driving purposes I will purchase a functional reproduction RC-15 from Tom DeWitt and if I ever decide to enter my Corvette into the NCRS judging events I will have a real RC-15 cap in my pocket.
Thanks to all for your comments and recommendations.

Scott,

I'd probably purchase a new RC-26 from GM (RC-15 not available anymore) and keep the original for judging. This is what I do on the 72. I've personally had poor luck with a reproduction.

Patrick

[Robert C.]

Re: Radiator cap restoration

Talking about the repro cap out there.... Big waise of time and money. They are so "wrong" !

[Patrick H.]

Re: Radiator cap restoration

Talking about the repro cap out there.... Big waise of time and money. They are so "wrong" !

Depends which of the 3 available versions you're looking at.
None is perfect, but some are better than others.

[D S.]

Re: Radiator cap restoration

Bob, wrong for their less-than-appealing appearance, function, or both? What does a person do who can't afford those pricey non-functional originals on eBay or don't have salvage yards to browse through? Here in Texas there are many salvage yards in small towns where caps can be found but finding one that actually holds pressure and looks nice at the same time would be rare. Is the answer to just buy a parts store radiator cap for driving function and put the original non-functioning cap on for shows? Just a rhetorical question with no argument for or against reproduction caps. But they do suck in appearance (and often in function) and despite much input to those who manufacture the reproduction caps they still won't tool them to exactly duplicate the originals.

[Tony H.]

Re: Radiator cap restoration

Sounds like a good time to jump into the conversation.

The analytical technique that I used to analyze the plating on the originals and restored radiator caps that were mentioned in the 2006 article is XRF which stands for X-Ray Fluorescence. This is a non-destructive test that allows identification of each layer of plating as well as the base metal. It can also show multiple constituents of alloys or mixtures of metals (such as brass which is a mixture of copper and zinc or 316 stainless steel which is composed of iron, cobalt, nickel, and molybdenum).

I have two restored caps, one from John Pirkle, one from Sal Carbone. Both are cadmium plated. The zinc and cadmium spectrums on the XRF are clearly distinguishable so I have no doubt whatsoever that these caps were cadmium plated. I have receipts from both restorers that reflects these purchases.

I have also analyzed original caps, several of which I borrowed and returned to their owners. Those caps always came up as a zinc plating. As Patrick stated, we believe all originals were zinc plated. The owners manuals for our cars further states that the radiator caps were zinc plated.

I agree that identification of plating metal by visual inspection is nearly impossible. Cadmium and zinc plating can look exactly the same given the right conditions of mechanical/chemical processing and lighting. Current technology allows us to make XRF analysis on the field using hand-held devices, but I doubt we will see that in the field soon, on a consistent basis, if at all.

As far as the changes to the manual, Patrick and I submitted rewrites but they unfortunately did not make the revision. I don't know why. Maybe they will make the next cut. The "silver" that I have noticed in judging manuals in past readings is usually stated as "silver cad" from my recollection. We have to be careful when we state a color because technically, they can mean something else. Silvery is different than silver and in my opinion, that distinction should be important in a TIM&JG.

[Barry K.]

Re: Radiator cap restoration

please excuse what may be a dumb comment/question here but if cadmium and zinc plating cosmetically look the same does it really matter what plating technique is used?
I understand that if the originals are zinc plated that many (most) probably want their restored part to be the same way but even if a restored part is done differently but cosmetically looks identical than where is the harm?
My understanding of NCRS judging guidelines is that the car and parts only have to APPEAR as they looked when the car was rolled off the factory line.

If cadmium plating and zinc plating both visually look the same than where does the difference come in as far as judging?

[John D.]

Re: Radiator cap restoration

please excuse what may be a dumb comment/question here but if cadmium and zinc plating cosmetically look the same does it really matter what plating technique is used?
I understand that if the originals are zinc plated that many (most) probably want their restored part to be the same way but even if a restored part is done differently but cosmetically looks identical than where is the harm?
My understanding of NCRS judging guidelines is that the car and parts only have to APPEAR as they looked when the car was rolled off the factory line.

If cadmium plating and zinc plating both visually look the same than where does the difference come in as far as judging?

Barry, I may have mislead you. Cad and zinc do NOT look alike. Nothing replaces the appearance of cadmium although the zinc without the blue is close but no cigar.And it doesn't age well at all. Many years ago a friend of mine worked at Robershaw and he used to Tin plate car parts for me. Not bad I thought in the olden days. I still have a small assortmen of hardware that I had tin plated.
Any experienced judge will be able to pick out fake cad in a heart beat. I know I can spot it at a glance and I don't judge that often. John

[Barry K.]

Re: Radiator cap restoration

If you can tell the difference between zinc and cadmium plating without a scientific analysis -- you are a better man than I am Gunga Din.

I agree that identification of plating metal by visual inspection is nearly impossible. Cadmium and zinc plating can look exactly the same given the right conditions of mechanical/chemical processing and lighting.

John
these were the statement made that caused me to ask my question........ you weren't misleading me.
Personally, I wouldn't know the difference between a cad plated part or a zinc plated part unless someone put both parts in front of me and showed and explained the differences.

[Tony H.]

Re: Radiator cap restoration

While some may feel they can distinguish between cad and zinc, I doubt most can 100% of the time. There are too many variables that affect the way something looks. The mechanical topography of a substrate prior to plating, the thickness of the coating, the pretreatment and posttreatment, as well as lighting may all affect the final appearance. On the other hand, the XRF and other scientific instruments have a much better batting average as far as nailing down exactly what and how much is there.

We "know" how it came from the factory. So, in our Technical Information Manual and Judging Guides, we should state what we "know" technically. As time and technology allows, we improve the TIM&JGs. When we restore something, we generally try or desire to make it like the factory, within our limited resources. Sometimes, perfection is not readily possible so we try to duplicate the look. In the end, we judge by appearance, because that's what we have, our eyes. If we had no sight, we might judge by touch, if we had X-ray vision, we might see things differently. As humans we have different visual talents. It's great if someone can distinguish between cad and zinc every time visually, but I cannot, so I use science. But, in the field, if it looks silvery cad, it's ok to me as a zinc plated part. And, for the most part, these caps were zinc plated parts.

[Patrick H.]

Re: Radiator cap restoration

Sounds like a good time to jump into the conversation.

The analytical technique that I used to analyze the plating on the originals and restored radiator caps that were mentioned in the 2006 article is XRF which stands for X-Ray Fluorescence. This is a non-destructive test that allows identification of each layer of plating as well as the base metal. It can also show multiple constituents of alloys or mixtures of metals (such as brass which is a mixture of copper and zinc or 316 stainless steel which is composed of iron, cobalt, nickel, and molybdenum).

I have two restored caps, one from John Pirkle, one from Sal Carbone. Both are cadmium plated. The zinc and cadmium spectrums on the XRF are clearly distinguishable so I have no doubt whatsoever that these caps were cadmium plated. I have receipts from both restorers that reflects these purchases.

At least I know that my memory isn't failing me.
I just couldn't find your XR spectrum and e-mail to confirm.
Thanks for the update.