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topic 49988

Cadmium Plating Problems

A discussion started in 2001 but continuing through 2020


Q. I'm doing some small-scale cad plating at home. I'm having problems with getting a "mottled" appearance. What am I doing wrong?


Mike M [last name deleted for privacy by Editor]
- San Francisco, California, USA


A. Hi Mike, Some hobby suppliers offer plating processes which are actually probably zinc or zinc-tin or some other alloy designed only to look 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, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha

Can't plate internal cavity

September 15, 2008

Q. We have parts we want to get cadmium plated; however, our vendors say they can't because of large internal volumes.

The parts are approx. nine inches long, have an O.D. of 8 inches, and an ID of 7.8 inches - the internal cavities are approx. 8.9 inches deep.

Our problem is that our vendors say they can only plate three or four inches deep inside the parts.

The base metal is E4340 - can anyone suggest a good alternative to cadmium plating for this material?


Jerry Smith
product designer - Huntsville, Alabama

September 15, 2008

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.


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

October 12, 2008

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

October 14, 2008

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

Cadmium plating roughness problem

October 18, 2011

Q. We have problem on cadmium plating in inside diameter (bore). The size is 3mm in diameter and 100mm in length. The specification said the roughness should be below 1.00 mm and thickness between 5-9 microns. We have tried to reduce current density to 2 Amps/dm2, but we still got problem, sometimes the thickness is unstable, also the roughness. We used auxiliary anode on bore made from steel. Is there any relation between rectifier ripple and loading quantity (total current used)?

Susie Susilowati
Engineer - Bandung, Indonesia

October 18, 2011

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.


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

October 24, 2011

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 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
Geoff Smith
Hampshire, England

Cadmium Barrel Plating is Gritty

gritty dangler in cadmium plating 49988
August 20, 2014

Q. We are experiencing problems with our cadmium barrel plating.

On removing and rinsing parts from the barrel, the finished parts are exhibiting minute particles (grain like) randomly dispersed on the surfaces. There are not embedded in the the cadmium plating but more so on the surface. We have to remove the particles using a fibre glass pen.

The contact bombs on the end of the danglers are covered in grainy particles (sand like) which I believe is contributing towards the particles on the finished components.
What is the reason for the grainy build up on the bombs. This occurs even after 1 or 2 loads. Is it because the bombs are sitting static in the barrel during processing.

Any suggestions as to how to solve this problem.

Many Thanks.

Nigel Bell
Process Engineer - Crumlin, Count Antrim,Northern Ireland

Nodule Problem in Cadmium Plating

October 27, 2017

Q. We run a sulfuric-acid cadmium process on steel substrates in two separate identical tanks (two plating stations each). We recently dumped one of these baths, suspecting it had become contaminated. Since we made this new bath, we are getting extreme roughness in the form of tiny nodules, which form everywhere except the underside surfaces, as the parts are positioned on the rack. Under magnification, these nodules look like tiny brown warts. If you scrub the area with a scouring pad, the nodules shine up like the surrounding cad plate surface.

nodules in cadmium plating 60554

We have ruled out cleaning. Parts from the other tank do not have this formation. Bath parameters for temperature, acid and metal content, etc., are in range and comparable to the other tank. No leaks identified. We filter these baths with .5-micron cartridges and have no detectable particulate in solution. Is this some sort of stress formation? So far the only difference we have detected between the two tanks is rectifier ripple: the roughness tank has 8%, while the other is only 1%. Even so, 8% doesn't strike us as alarming, but we are working to bring that down.

We use iridium-oxide inert anodes (instead of graphite), and our cadmium anode baskets are bagged.

Any ideas? Our chemical reps have all but given up.

Bruce Brady
- Lincoln, Nebraska, USA
  ^- Privately contact this inquirer -^

CADMIUM PLATING: Rough/ Nodule surface problem

August 27, 2019

Q. Hi.
I'm doing Cadmium plating (DULL FINISH) for almost 4 years.
Lately, the roughness of the surface doesn't meet requirement.

Condition of cadmium tank:
a)NaOH: 20 g/L
b)NaCN: 108 g/L
c)sodium carbonate (washing soda) [affil. link to info/product on Amazon]: 34 g/L
d)Cadmium metal : 30g/L
e)Working temperature: 25 degree C
f) Filtration: YES, solution continuously filtered through 5 micron string wound cartridge filter.
g) Already done dummy plating for 36 hours at 4amp/dm2. But the result (appearance) still no good (see picture).

Material to be plated is steel and stainless steel. For stainless steel Nickel strike has been done before start plating.

Before going to plating tank, alkaline cleaning, electro cleaning, activation has been done to the parts.

I really need help regarding this issue.

Thank you for your help.

Izzuddin Jaafar
- Selangor, Malaysia

Cadmium anodes turn black only during plating

February 12, 2020

Q. What would cause a black film to form on cadmium anodes while plating that would dissolve very rapidly off the anodes when plating is complete.

Don Davis
American Airlines - Tulsa, Oklahoma

February 2020

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


pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

simultaneous February 12, 2020

Q. The plating solution in respect to the post is LHE cyanide cadmium. The film does not seem to effect plating efficiency or HE.

Don Davis [returning]
American Airlines - Tulsa, Oklahoma

February 12, 2020

A. In a common cyanide cadmium solution the anodes turn black when the free cyanide is too low. Get it back up to about 18 oz/gal and the metal around 3 oz/gal, try it in a bucket first and see if the black goes away and you see clean cadmium color.

robert probert

Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

March 2, 2020

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

No cadmium plating coverage on large or rough parts

September 14, 2020

Q. We have encountered a problem with our cyanide cadmium plating. After 20 mins of plating with 25-35 °C temperature and 2-5 Amps, still the plating is missing on several parts of the job. Plating happens well on small and smooth surface parts but not on un-smooth surfaces and large parts. Keeping in mind that the job is well stripped and degreased before plating. We have some critical jobs pending I would like to hear your valuable opinions.

Zeeshan Ahmad
- Islamabad, Pakistan

September 14, 2020

Q. We analysed this specific bath and the analysis result shows that every content of the bath is in range. The composition of the bath is mentioned below.
Bath composition :-
Solution Volume :- 576 litres
CaO : 35-40 g/ltr
NaCN : 90-120 g/ltr
NaOH : 20-30 g/ltr
Additives: NiSO4 : 1kg

poor coverage in cadmium plating 49988-2a   poor coverage in cadmium plating 49988-2b   poor coverage in cadmium plating 49988-2c   poor coverage in cadmium plating 49988-2d  

Zeeshan Ahmad [returning]
- Islamabad, Pakistan

October 12, 2020

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

Ed. note: This is only one of 60,000 threads on finishing.com; we have several threads focused on specific cadmium plating problems like topic 47214 "Cadmium plating turning black" and topic 36051 "Cadmium plating blistering/adhesion problems". Please search the site for "Cadmium plating [specific problem]".

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