Cadmium Plating Q&A Problems & Solutions

A. Hi Mary,

This looks to me like it may be cadmium bloom, which occurs when cadmium reacts with certain organic acid vapors. The most common cause for this is improper storage in certain types of wooden containers. Heat and humidity can cause vapors from the adhesives to diffuse into the air and react with the exposed cadmium. Be very careful! Cadmium is a dangerous poison, and those white crystals can form an inhalable dust when handled.

Luke Soleim
- Minneapolis, Minnesota
October 6, 2023

A. Some hobby suppliers offer plating processes which are actually probably zinc or zinc-tin or some other alloy designed only to look a bit like cadmium plating ... while not actually containing any cadmium. Hopefully that's what you really have because the answer to your question of "what am I doing wrong?" is "cad plating at home"! Sorry :-(

Cadmium is a biocumulative poison like lead and mercury, with very similar effects on development. For that reason, it is the law that every worker doing cadmium plating must have their blood periodically tested for cadmium by a physician.

Also, when your rinsewater becomes contaminated, if the city finds you disposing of it in the sewer system, you may find yourself in more trouble than you could possibly believe. Cities periodically sample the sewers for cadmium to track it to its source because of its tremendous and cumulative toxicity, and if their sludge has cadmium in it they must dispose of it in a hazardous waste landfill which costs them a fortune.

Then there is the question of what you will do with the cadmium plated parts. Only the most critical military and aerospace parts are plated with cadmium these days in the USA, and cadmium is completely illegal in Japan and many countries. If your parts somehow eventually found themselves into food service, say on a backyard barbecue grill, it would be very dangerous; there are cases of whole families being seriously sickened from using old cadmium plated refrigerator shelves as barbecue grills.

This finally brings us to your "mottled appearance" problem. No supplier or consultant anywhere is going to assist you in troubleshooting the problem because of the liability. I am having trouble imagining where you were able to buy cadmium anodes and cadmium plating solution as I thought that no supplier had shipped cadmium chemicals to a residential address for decades now. Unfortunately, you also have a major disposal problem as it may cost you thousands of dollars to dispose of even a relatively small cadmium plating bath. Cadmium plating, when vital for critical components where substitute plating would render them dangerous, must only be done in a proper industrial facility. Again, hopefully you're working with an imitation, not actual cadmium -- in which case, ask the hobby supplier for guidance because we don't even know what metal or alloy it is. Sorry again :-(

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. What does HND stand for? Cadmium can be plated in barrel or rack, or portable by brush plating. See a text on electroplating for specifying equipment. Cadmium, with it's toxicity problems, has been slated for replacement with other coatings.

  
Tom Pullizzi
Falls Township, Pennsylvania

A. Please be aware that Cadmium electroplating should not be used in any space application due to outgassing problems in a vacuum. As long as the parts will not go into space there is not a problem except, as stated in a previous answer, there could be environmental issues with the cadmium itself. A few years ago cadmium was banned from a lot of military and commercial applications due to potential toxicity concerns.

David Jones
- Canyon Country, California, USA

A. Hi, Jerry. We have many threads here about possible substitutes for cadmium plating; please put "cadmium plating alternative" or " ... substitute" into the google custom search engine to find those many informative discussions. But the thing is ... obviously, nothing has ALL of the properties of Cadmium, and substitutions can only be suggested with extreme care after understanding the full functions of the component.

The problem here is not cadmium plating specifically, but economical plating of an internal cavity. Parts shaped like a topless box are plated all the time; it is possible to cadmium plate these parts ... but perhaps not within your budget. Internal anodes will be required, and perhaps additional handling, like plating with the open end of the hole up, then inverting to minimize dragout, etc. Best of luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. It is possible with additional anode to be given in ID. We are following the same for aerospace components and we are getting the same. If require You can go for even local plating also.

T.Chandra Sekhar Reddy
plating shop employee - Mumbai, Maharashtra, India

A. This is not an easy part to plate, so many platers will pass upon the opportunity. It has to be run on a hand rack since it must be plated with the opening up to avoid gas generation being trapped. Parts this size are bulky/heavy which slows down production. It will require several racks made especially for the part. It WILL require an internal anode. Stick cadmium for anodes are very difficult to come by. We ended up casting our own which is a safety problem. Cadmium fumes are toxic!.
Why cad? You might be able to use zinc. EN might work, but would be more costly. Silver is an excellent replacement for cad for most uses, but that is really expensive.

James Watts
- Navarre, Florida

A. Hi, Susie.

Even with an auxiliary anode it is difficult to plate a 3 mm inside diameter 10 mm long because the limited amount of solution inside the diameter can go out of balance very quickly. My suspicion is that the solution is way out of balance long before you've achieved your 5-9 micron plating thickness. I think you will have to force solution flow through the cavity.

Depending on the type of rectifier, operating at a low percentage of capacity can produce extreme ripple. Any rectifier that "chops" the input power as opposed to transforming the voltage (which is most rectifiers today) will suffer this problem. Still, my guess is that this is not the main issue causing the problem that is confronting you. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Susie
The first thing I would check with a roughness problem is the state of the filters and look for any holes in the anode bags.
The easy to check for particulate contamination is to get a beaker [beakers on eBay or Amazon] of solution and shine a beam of light through. Viewed from the side it is quite a sensitive test. Do a search on "Tyndall effect".

Geoff Smith
Hampshire, England

A. Hi Don. This might depend on whether the bath is cyanide, acid, Ticad, LHE ... so it would be helpful to know. Thanks.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Maybe it's turning black because you apply high (very) voltage? After you switch off, the anode turns to normal?

Izzuddin Jaafar
- Selangor, Malaysia
March 2, 2020

A. Hi. I try to give my opinion.

What is the material of the parts?
What is required thickness of the plating?

My opinion,
Plating current is not enough. 2-5 Amps is to low for big parts. It's working well in small parts, but not in big parts, since your surface area already changed.

Use CURRENT DENSITY (need to calculate to set your current based on surface area of the part) between 20-30 ASF (ampere per square foot).

Refer to the jig picture, it was difficult design for me. It is better to use one hook jig only, and try to rotate the part in interval time of five minutes.

If, after applying above steps, you need to setup new anode that located at the very deep area (plating hard to reach/ cover).

Thank you.

Izzuddin Jaafar
- Selangor, Malaysia

A. Hi. If the wetter doesn't relieve the pitting, I'm guessing they are not gas pits (which would be hemispherical and shiny). But if they are, and they are also on the Hull Cells (which don't get exposed to any polishing/buffing changes you might have made), then it remains as something wrong with the wetter. Are you able to do dyne testing?

A good close up picture of the pits would probably help get us all on the same wavelength, but if the Hull Cell panels do not enter your standard pretreatment baths, clearly the problem is in fact with the cadmium plating solution.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. No, it looks like he did not neutralize the cyanide plating solution before going into the yellow chromate solution. Good practice requires a weak nitric acid dip ahead of the yellow chromate, but most job shops do not maintain the acidity of the weak nitric pre-dip.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina