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Cadmium plating fasteners as part of a restoration has been growing in popularity in recent years. There are many good reasons to cad-plate and very few reasons not to spend a bit of extra money to protect your fasteners. The first restoration project on which I heard of cad-plating was a Porsche 356 in 1989. At the time, Harry Pellow of HCP Research in Santa Clara, California was building the very best Porsche engines on the west coast, and he swore by cad-plating every fastener on the engines he sold.
The reasons to use cadmium plate boil down to protection and reliability. The cadmium layer goes on thin and the plating is soft and malleable enough that it won’t cause any trouble with the threads on your hardware, but it strongly resists corrosion even in salty environments.
Unlike steel, cadmium is not subject to galvanic corrosion when placed in contact with aluminum in a salty environment, so you avoid adhesion problems down the road. This is the biggest reason why plating brackets and supports with cadmium is popular, especially in marine applications or if you live near the ocean or in any environment where you might encounter salt on the roads.
Unlike many harder plating surfaces, cadmium-plated bolts can be reliably torqued because of the softness of the coating. However, many charts recommend reducing the torque specification of a cadmium-plated bolt by up to 25%. Research this carefully and talk to your plater and other experts before altering the torque spec on any critical application.
Cadmium-plated items can also be painted and will hold the paint like a primer. Finally, you can dye the cadmium plating to several nice tones, or put it on clear to maintain the color of the underlying fastener or part.
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Warning... |
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No process is free from its tradeoffs, however, and cadmium’s tradeoff is toxicity. Cadmium is poisonous and must be handled carefully. This is why all cad-plating should be done by professionals. Any plater who is working with cadmium in a metropolitan area is subject to extensive environmental regulations, so you can use them in good conscience. It is not dangerous to you to use cadmium plated parts, but keep them out of your mouth, and don’t grind them or heat them to the point where they might outgas and you might breathe the fumes.
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Another protection process often used is zinc plating. Zinc oxide makes an excellent protective layer, and in the event that the protective zinc layer is breached, the zinc layer becomes a sacrifical anode and will corrode and decay before the underlying base metal can be affected. Many of the fasteners you purchase are already plated with zinc for this reason. Like cadmium-plated fasteners, many torque specifications are reduced by up to 15% for zinc-plated fasteners, but check with your plater or other expert source to make sure that the provided torque specs have not already been reduced to account for zinc-plated fasteners.
You can find kits and supplies online that will allow you to perform your own plating in a home workshop. These kits can work well, but many restorers have had mixed quality in their results. Especially when working with toxic materials such as cadmium, it’s still better to use a professional shop. However, one variation on plating that you can do at home with a kit is to copper or brass-plate small parts. This is very helpful if you’re restoring a brass-era car and the malleability and availability of copper makes this a fun do-it-yourself project. Just don’t try it the first time on an irreplaceable part!
A related process to plating is tinning. However, with this method of coating works by dipping the part into a vat of molten tin, which allows the metal to coat the part more thickly. Preslee Jeffers of Action Metal Stripping in Hubbard, Oregon performs this service for restoration customers.
“We do hot-dip tinning. It’s pure tin, and a lot of people bring their gas tanks in, and we take all the solder out of them, take the neck fillers out, we clean them, strip them and get all the oils, gasses, varnishes, and undercoatings and debris, run them through a flux and submerge it in molten tin. We pull it back out, solder the neck filler back on, solder up any holes, and then pressure test them. You can tin just about anything. It costs $300 to $400 to tin a gas tank,” Jeffers says.
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DO |
- Take your fasteners to a well-regarded professional plating shop
- Look carefully at the plating shop. Plating is a precision process, and the shop should be clean and orderly
- Ask your club or other local restorers for references to a good plating shop
- Look into zinc plating as an alternative to cadmium
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DON’T |
- Don’t place cadmium plated washers or nuts in your mouth while working
- Don’t arbitrarily reduce torque specs without research
- Don’t grind or weld on cadmium plated parts
- Don’t try home-plating important parts without practice
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When I started putting the Packard’s chassis together I quickly realized I didn’t want to clean and coat the fasteners one at a time. Also, I didn’t want the Popular Restorations feature car’s fasteners to ever rust again, at least not in my lifetime. I had about 200 baggies of nuts, bolts, screws, washers, springs, etc. Using chemical baths to remove grease, rust, and paint can take days. So I bit the bullet, photographed the fasteners, and then combined them in a large plastic bucket.
The dipping process at American Metal Cleaning took a number of days, but when they were done the fasteners were sparkling clean.
After some research I decided to plate the fasteners with cadmium. I chose cadmium because of its appearance, its long-lasting, protective nature, and because of its lubricity--cadmium fasteners are less likely to seize than with zinc.
Next, I transported the bucket to East Side Plating for barrel plating. That means they were put in a rotating barrel during the plating process. I think the price was something like $100 for up to 70 pounds of parts. What a deal!
The only problem was that when I got them back, it took hours to sort them into general categories such as lock washers, countersunk screws, large fine-threaded bolts, etc. I used four Stanley parts organizers which helped a lot. But I’ll have to be honest, I spent many hours during the assembly process trying to figure out which bolt went where. It’s one thing to have notated photographs of the baggies of fasteners. It’s another to find those fasteners among hundreds that look nearly alike. What saved me though was having a factory parts manual.
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Rob Pyle, Inside Sales Manager
8400 Southeast 26th Place
Portland, Oregon 97202-8946
1-800-394-8554 or (503) 654-3774
www.eastsideplating.com
PR: Do cadmium plating customers need to pre-clean their fasteners and brackets?
RP: The first thing, we need to find out the condition of the materials. Do they have old plating on them, or paint? We have to treat those separately and strip whatever’s on the parts prior to replating. If there’s paint and plating on them, we have to remove the paint prior to putting it in our strip tank for the plating. That plating has to come off, because if you try to plate over old plating, you won’t get good adhesion. You can save some if the parts are clean of dirt and grease, but the parts have to be 100% clean down to the base metal.
PR: Cadmium is a toxic metal. How do you deal with that?
RP: Cadmium is considered a toxic metal. It’s banned in some European countries. The main thing is that after we strip cadmium, we have to waste treat the residue and then the metals are recycled.
PR: Are restorers being exposed to toxicity by using cad-plated parts?
RP: We’ve never heard of anyone being poisoned by cadmium. We do recommend that you use gloves when handling the parts, however. You wouldn’t ever want to weld to cadmium, because it will create a gas you don’t want to inhale. It’s more of a long-term exposure kind of thing.
PR: What about zinc plating for original-looking parts?
RP: We can do that, and also black cadmium and zinc plating for original-looking parts. We also use a bright zinc, and then we can apply a clear or yellow or black chromate coating.
PR: What’s the lead time to plate a car’s worth of small items?
RP: Two to three weeks.
PR: About how much should people expect to pay for all the fasteners and a few other parts on a restoration?
RP: Depending on the amount of cleaning required, anywhere from $200 to $300. If you’ve just got fasteners, we can barrel-plate them, but if you’re talking about bigger parts, we have to rack them. It can get a lot more expensive if parts have to be stripped and racked and taken to a handline. It’s not an inexpensive process because of the waste disposal and recycling.
PR: How can customers control their expenses?
RP: When the customer brings in the parts, we give him a price right up front. One thing with people who specialize in restoration of cars is that they can save money by stripping the paint off themselves and bead-blasting the parts. Once their clean they can look at the parts and assess the damage to the base metal of the parts. So they can make a decision about whether they want to plate that part or get a new one.
PR: Any other advice for restorers?
RP: The most cost-effective finish is zinc-clear or zinc-yellow. Cadmium in a barrel is also a lot more cost-effective than cadmium on a rack. But one other thing is that in any plating process, there are hardened spring steel parts that have to be baked after plating. During the acid bath, those parts absorb hydrogen and can become brittle. We bake those parts for 4 hours to release any hydrogen that was absorbed during our process. Parts can break right in half under stress if they’re not properly relieved. Finally, take an inventory of your parts before you bring them in. We don’t like to lose parts, but it can happen. If something like that has happened, we then know what we’re looking for.
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| Click on any item below for more details at Amazon.com |
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Dennis W. Parks
How To Plate, Polish, and Chrome
Motorbooks, Paperback, 2006-11-15 |
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Aluminum and steel can be polished, chromed, anodized, plated, and painted, and this book shows enthusiasts how to do it. The book includes what is required, what it will cost, when to use different processes and whether to have a professional do it or tackle the project at home. Applies to cars as well as motorcycles.
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Mike Mavrigian
High Perf. Fasteners & Plumbing HP1523: A Guide to Nuts, Bolts, Fuel, Brake, Oil & Coolant Lines, Hoses, Clamps, RacingHardware and Plumbing Techniques
HP Trade, Paperback, 2008-01-02 |
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This user-friendly guide explains high-performance fasteners, plumbing, and all the other hardware used by racers, rodders, restorers and all other auto enthusiasts. Subjects include hose sizes, fittings, materials, routing and installation tips, heat shielding, brake, fuel, coolant, and oil lines, as well as fastener technology such as thread sizing, clamping loads, bolt stretch, and fastener styles.
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Eastwood Electroplating System - Tin Zinc Plating Kit
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Plate almost any metal part at home including brass, copper, and steel (not for aluminum, pot metal or stainless steel). The Tin-Zinc Electroplating System brings a brilliant luster to properly prepared metal parts with a corrosion-resistant, protective plating resembling chrome but without the expense, hassles or hazards.
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