Metalurgists - Educate Me Please...

[Wayne 962]

There are a few things that stick in the back of my mind that have confused me for many years. One is cadmium plating (cad-plating). Okay, I've got a mess of old batteries that are NiCad (Nickel-Cadmium) and on the side they say that cadmium is a cancer-causing, very toxic metal.

The nuts and bolts that come from Porsche are plated. People commonly call these cadmium plated. Likewise the same nuts and bolts that come from Wurth are called "yellow-plated."

Someone want to tell me what they are talking about? Are these really cadmium plated with this toxic metal, or plated with something else, and it's a term being used, that's not exactly representative?

Inquiring minds want to know.

-Wayne

[thomschoon]

"cad" plating has pretty much been replaced by zinc which has a dye added to give the color (same as for cad parts). In some industries chrome was reduced by going to nickel sulfamate or thermal spray. The goal is to reduce the amount of heavy metals leaching into the ground water as well as the exposures from application and use.

Not a metallugist, just spent a few years at a large aerospace company trying to figure out how to keep ahead of the regulators both domestic and EU.

[Wayne 962]

So, does that mean that the original plated nuts on the engines from the late '60s still contain the toxic metals?

-Wayne

[TerryH]

I'm not sure what you're getting from Porsche, but cadmium is akin to mercury and lead. It has an accumulative effect after exposure. There have been efforts in the past few years to get rid of or at least, curtail its usage.

[Chuck Moreland]

Not a metelurgist but I play one on tv, and I've had lot's of stuff plated.

My understanding is the original cad plating on Porsche parts was indeed cadmium. Cad plating has all but been regulated out of existance in the US and I beleive this is true of Germany as well.

The replacement is yellow zinc dicromate. That wurth calls their new parts yellow plated sorta suggests it's yellow zinc.

[Wayne 962]

How can you tell if it's cadmium versus the newer yellow zinc?

I guess I better stop licking old bolts.

-Wayne

[Doug Zielke]

Thom is on target with his post.

A local plater I use on a regular basis told me the same.
They used to do a lot of actual Cadmium plating. Then environmental and other gov't regs made it too costly to continue using Cd.
It's deadly *****.
The last batch of parts I had done there for a m/c restoration, was zinc with a dye, as previously mentioned. They call it "Yellow Cad", but there is no Cd content at all.

[Chuck Moreland]

Originally posted by Wayne at Pelican Parts
How can you tell if it's cadmium versus the newer yellow zinc?

I guess I better stop licking old bolts.

-Wayne

Scrape it with metal. Yellow zinc comes off relatively easy.

The appearance is a bit different too. Cad looks deeper, and richer gold tone.

[Quicksilver]

A note from the welding side of things...

You never, ever weld something that is cad plated. It releases toxic gases. The aviation industry sends it to the plating shop to have it unplated before welding. After welding they send it back to be replated.

---
Just a guess. I would suspect that the cadmium from plating is probably very stable which is why it was a good choice for plating to begin with. The cadmium in a battery is specifically designed to be mobile as the cadmium is transferring back and forth between the electrodes when the battery is charging and discharging. Also I would guess that there is a certain quantity of cadmium suspended in whatever is used as an electrolyte and that would be extremely mobile.


Wayne

[Fishcop]

I am thinking of investing in my own "home plating" system. Here is the link with some good info http://eplate.com.au/ tell me what you think.

[midlife]

Warning! Driving a Porsche causes cancer.

I think the danger with Cadmium is only in processing, or possibly leaching out in the landfills. I don't think handling bolts will hurt you. Most auto makers got rid of Cad plating in the late '80's or early '90's.
Now the latest craze is to get rid of all Hexavalent Chromium. (Thank you Erin Brokovich.) This is found in most platings including the yellow Zinc Chromate. This ban keeps getting delayed do to a lack of low cost alternatives.

Originally posted by Wayne at Pelican Parts
I guess I better stop licking old bolts.

-Wayne

Licking your bolts is OK, but licking your nuts would be really impressive....


I'm so sorry, I just can't help myself.

[midlife]

One theory is, that if we could lick our nuts, we would never have developed speach. Take dogs for an example.

[Eugene at Pelican Parts]

Umm... what are the factory spring plates plated with?

Let's say someone were to clean them up with a wire wheel without wearing a face mask. Would that someone eventually grow fingernails in funny places?

[bigchillcar]

I see a lucrative class-action lawsuit here to take down "Big Cad." Where did Al Gore go?

didn't al gore invent cadmium?
ryan

[KFC911]

When I refreshed my suspension, I was able to get everything gold cadmium plated by someone who's business was 'grandfathered in' here in NC. The 930 rotors wouldn't fit in his 'cad tumbler', so he used yellow zinc dicromate on them. Here's a pic (testing out Wayne's new 'pic resizing feature') showing the difference in appearance:

[Grady Clay]

Wayne,

The original plating Porsche used was just cadmium. It had a dull silver color and took on an almost “fuzzy” appearance when it had been out in the weather for some time.

In about ’68 Porsche added the “chromate conversion” process to the cadmium plating and produced the gold color for the first time.

In the late ‘80s the cadmium was eliminated and the zinc with gold dye replaced it. With two gold color parts next to each other the color difference is very apparent.

I can send you some virgin cadmium-chromate conversion parts if you want.

Best,
Grady.

[RickM]

When I had many pieces done it was called Yellow Dye Chromate. It appears it goes by different names. Also, my understanding is that these two processes are cheaper alternatives to chrome plating and that's why they were/are used.

Is Cadmium a sacrificial element as Zinc?

[First911]

I work in the environmental field and have done several investigations and cleanups of former plating shops. They can be nasty. However, the biggest environmental concerns are most often the chlorinated solvents used to degrease metals prior to plating and not the plating solutions themselves.

The EPA and Cal-OSHA have calculated "acceptable" exposure doses for just about every chemical assuming a variety of different pathways: dermal contact (through your skin); inhalation, and ingestion. If you can protect these pathways, you eliminate or greatly reduce the risk of chemical exposure.

Cadmium is known carcinogen, but its toxicity is much less than other metals like hexavalent chromium or beryllium (for you high-end bicycle racers). You can eliminate almost all of the risk from handling cad-plated hardware by wearing any type of gloves (and wearing a face shield if you're grinding on them). Toxic fumes from welding metals are hands down the biggest health risk from metals. If you do a lot of welding, I'd get a half-face respirator with cartridges for metal fumes to fit under your welding hood.

The bigger health risk for the Porsche enthusiast in my opinion (aside from the extreme wallet-draining capacity of tinkering with these cars) is from volatile organic compounds contained in the gasoline, parts cleaning solvents, and paints used. The lungs are much more susceptible to damage than the skin. There is a far greater health risk from breathing brake cleaner fumes (its full of carcinogenic PCE also used as a dry cleaning solvent) in a closed garage than handling a few cad-plated nuts and bolts.

Adequate ventilation in your work space will help tremendously to reduce health risks during welding or using chemicals. Open the doors and/or use fans. Don't trust your nose because it often gets de-sensitized after prolonged chemical exposure.

If you are using a lot of chemicals, I'd wear surgical-type gloves, but make sure they are rated for chemicals. Most chemicals used in the garage will go right through the white rubber surgical gloves. Nitrile gloves (usually blue in color) are much better.

Sorry for the long post, but this is what I do all day. I'm no environmental zealot, Green Party, Sierra Clubber. I grew up washing car parts barehanded in gasoline and learned to use used motor oil for weed control by pouring it on the ground along our property boundary (thanks Pop). You can go to jail for dumping oil now - so please recycle!

I'm sure I got more chemical exposure wrenching on cars than in 20 years of working on "hazardous waste" and Superfund sites. So far, no health issues (knock on wood). Next time you see somebody in a moon suit next to a drill rig, it could be me.....

[Cobalt]

I have to agree with RickM. The surface treatment otherly known as chemical conversion is a Dichromate treatment (also known as pickling). There are many different treatments depending on desired results that may be used. It is used to prevent corrosion. There are several MIL or AMS specs that apply to these processes.

One type of treatment put in simple form is an acid solution (usually Nitric) mixed with Sodium Dichromate, and a small percentage of either Sodium, potassium or ammonium acid fluoride. The acid etches the surface and the dicromate bonds to the surface leaving a protective coating.

Depending on the required end result sometimes these treatments are preceeded by an Anodic treatment. This is accomplished as a one step treatment employing an aqueous ammonium bifluoride bath in which alternating high voltage currently generally produces a uniform clean white or yellowish appearence. The color can vary based on the chemical composition of the alloy and the hardness. Usually after this type of treatment the parts are dipped in a boiling chromic acid pickle solution for 1 to 15 min and then rinsed in cold water.

I do not work with steel parts so I do not know the exact application for steel. However this works on Magnesium and the process for steel varies but is similar.

I hope this helps.