Pits in Nickel/Gold Plating

A. Certainly gold plating which does not deteriorate in a short time is something which is commonly done. Typically this might be a thin nickel underplate and 0.00005" or more gold.

The condition you describe may be typical for this manufacturer's work, but you can see gold plated costume jewelry everywhere which lasts for years.

A. Usually those parts are nickel plated before the gold plating. Naturally the gold is thin and soft. But for it to start pitting makes me think there is little or no nickel underneath the gold. I have worked on guitar parts before and have found this to be the problem described. Take your parts to a reputable plater and get them done correctly.
Best regards, Frank

A. Thanks, Jeffrey & Frank.

Gordon, I bought a Gretsch Anniversary Model way back in college in the late 60's. Everything was all nickel plated and I kept it for 25 years with no tarnishing, and indeed there is nearly always nickel plating under the gold plating. If your complaint was that the gold was wearing off too fast, well, people do keep reducing the thickness of gold plating on things ... but if it was properly nickel plated (as Frank notes) it wouldn't pit regardless. The pitting indicates porosity in the nickel plating because it was improperly done (was probably too thin).

opinion !   Consumers: you have friends & supporters here rather than adversaries; we don't like it at all when shops cut corners and the plating is unsatisfactory. When plating is defective, it's defective regardless of what the manufacturer feels or claims! They get to choose whether to call what they sell you a 'manufacturing defect' vs. a 'design defect' or whatever -- but they don't get to decide that crappy plating is "perfectly natural" -- it absolutely is not :-)

Luck & Regards,

A. Have you considered ditching the carbon filters? They'll remove the wetters, and may be a source of nodules if the filter quality is poor. You might try going to a plain polypropylene filter with no or removed sizing. Make sure that the filter is suitably fine for your operation ... I never used filters coarser than 10 micron absolute.

A. Hello Joy,
Pitting can be caused by different factors. Usually caused by hydrogen gassing or oil / grease introduced to the solution, or poor cleaning. If it is a hydrogen gas bubble, the pit will usually have a tail (from the gassing). This is most noticeable in the high current density area. Certain measures can be taken.
1) Use an air blower, not compressed air for agitation. If compressed air, it should be oil free.
2) Check above the tank, make sure no grease or oil can drop into tank. Be sure no oil is floating on pre - plate tanks (drag-in possible).
3) Be sure anode bags are clean, come up above the solution level, and tied around the anode hooks.
4) If you are still using air agitation, check with your supplier to be sure you are using the proper wetting agent. The wetter varies from air agitation to solution agitation.
5) Investigate your cleaning cycle, do a water break test after cleaning.
Nodules are normally caused by poor filtration whereby particulate matter is suspended in solution. Nodules and pitting are not related.
It sounds like you are running a lot of carbon packs in the bath. Carbon polishing should only be done periodically. You could be filtering out an additive that you need. Good Luck!

A. Hi. Mark's advice is better than any I could give; I'd just add that 'gas pits' he mentions are invariably hemispherical and bright, which helps distinguish this problem from other causes.

Luck & Regards,

A. Joy,
The main cause of pitting is hydrogen gas adhering to the surface during plating.
Make sure you have adequate bath agitation, and are employing the proper current density. Also make sure the boric acid concentration is within range. Organic contamination generally is not the cause of pitting. Is your supplier helping you with this problem?

A. Specific recommendations on filtration/mechanical agitation depend upon the physical plant as much as the process and parts involved. I still kind of think 3/week carbon polish is somewhat excessive, but that would depend upon exactly how you do it and how big the tank is, etc.

Some small rules of thumb I've used: You need to size pumps to provide about 4 tank turnovers per hour. I've generally used about a 3 cm stroke for mechanical part agitation, and sufficient air to raise the solution level 3 cm (air might/might not be appropriate, depends on the wetters).

A. I understand that without the Carbon filter, the plating parts will have crack issue which normally result from organic contamination. However, doing Carbon treatment will not only remove the contamination but also the wetting agent as well.

However, there is a carbon filter that removes organics selectively. It will only remove the contamination while still retain your wetting agent and brightener. This product is from Japan.

You can try to use the special carbon filter continuously to remove the organic contamination while still maintaining the additive and wetting agent. This filter works well with some products but you will need to test it out with yours.

Note that wetting agent only helps to prevent the pit issue, you will still need to consider the agitation and other factors too.

Hi, Robin; hi, Melchor. Even better would be to get a patent number or an explanation of what they are claiming. Some brighteners are removed by conventional carbon filtration, some are not; some breakdown products are removed, some are not. It would be great to get a technical handle on what Robin is talking about here. Thanks!

Regards,

A. Hi Melchor,

This product is manufactured by Japan.

I am not too familiar of the theory of this specific cartridge but it is supposed to remove a specific range of organics. Although this product is designed to selectively remove organic contaminants, it will still remove some good organics (brightener) in your solution. This product is normally used only in the Nickel plating process.

Good Luck.

A. Hi BC. I suppose that on some occasions SEM images can be helpful in diagnosing the cause of a plating problem, but my personal opinion of them is (as we say in the US idiom), often "you can't see the forest for the trees".

I don't know what the magnification is here because the photos are too small and low resolution to read the text, but I'm not even sure that what we see in the plan view indicates anything wrong. The cross-sectioned micrograph does seem to indicate that the top layer of plating has not filled all the crevices in the metal below it, but again, not knowing the magnification or what I'm looking at, it's hard for me to comment at all :-)

Hopefully, someone who spends a lot of time studying SEM images might be able to make more of them than I am able to, but what is the evidence that the plating is even defective? And if it is, I don't see how the SEMs tell us whether the problem was poor mechanical finishing, cleaning, activation, or what -- sorry.

What are you plating and why? What is the specified thickness of the nickel plating and of the gold? Thanks!

Luck & Regards,