White patches in Chrome Plating

A. Hi Travnickova.
Maybe better incoming inspection? I don't think the missing plating is a nickel-chrome plating defect, but bad material or at least not properly cleaned?

But that's only a guess because we have no information at all yet; not even what the substate is nor any data about the plating. It's hard to know if the roughness everywhere is burnt plating, or parts which received no mechanical finishing :-) Luck & Regards,


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

A. Hi

Safranek's book has an excellent chapter on inspection stations, including lighting ⇨
Luck & Regards,


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

A. Hi Norddin,

Non uniform white patches could due to:

1. Lead contamination in chrome bath.
2. Poor cleaning prior nickel plating.
3. Part dries prior to chrome plating.

Regards,
David

A. Hi Chandrashekhar. Sorry, I'm not sure if I'm fully understanding your question. Are you saying the patches form in the semi-bright nickel plating step, but then you go on to bright nickel plating and chrome plating and you can still see them after the other plating steps? Apologies, but I don't quite understand your situation. Please spend several paragraphs on details. If you can include pictures I'm confident that the readers can help you address it. Thanks!

If you are seeking a general discussion of nickel plating issues, like what effects the semi-bright nickel step can have on the final nickel-chrome plated object (with all the ifs, ands, & buts), here is a nickel plating book which should help. The Canning Handbook [on eBay, Amazon, AbeBooks] has a good troubleshooting section on nickel plating too. Good luck.

Regards,

A. Hi Gaurav,

The problem could due to:

1. High pH
2. Low wetting agent
3. Low chrome concentration
4. Lead, zinc contamination
5. Poor cleaning before plating
6. Parts dry up prior chrome plating

Regards,
David

A. The rinses between nickel and chrome contain inorganic contamination.

Regards,

A. Check the sulphate ratio. It is common when sulphate ratio is high in the bath.

KP

Thank you for your opinions but I think it's something wrong in the nickel bath because when I add 0.1 mL/L of brightener and/or some wetting agent the white spots usually disappear. We have problems with these white patches only on bright nickel not on matte nickel.

A. I have a strong feeling that the bright plating tank/vat may be contaminated with oil hence these patches. Please use scum remover, or use filter paper and swipe over the top of the tank, and use carbon treatment more periodically. Best regards.

Hi Lawrence. Tin-lead and antimony-lead anodes were successfully used for chrome plating in thousands of shops for decades before I entered the industry, and that was 50 years ago -- so I would be shocked if they are the cause of white staining ... but I can't argue with your findings.

There may be something wrong with today's anodes or something unusual about your situation. Thanks for the thought-provoking idea !

Regards,

A. Good day Lawrence.

This white staining reminds me of "white wash". We could buff it out. In my experience, this "white wash" was attributed to organics carried over from bright nickel, and passivation of the nickel plating. High wetters/brighteners are difficult to rinse, and you need to avoid passivation of the nickel plate. I have used a nickel drag out tank, and kept the pH acidic, in an effort to simulate an acid dip. The drag out was sent to waste treatment weekly, as our sludges were sent to refining = $$$$$ in nickel metal. Also, I used the chrome drag out before chrome, but this drag out needs to be also kept clean. Are you using silver oxide? Are you adding barium carbonate as a slurry in water before adding to the chrome?
Just a few thoughts.

Regards,

  Hi Sanjay. Please send pictures to mooney@finishing.com for posting here. One person's "water mark" can be another person's "whitewash", someone else's "patches" and yet another guy's "skip dots". Thanks.

Regards,

A. Hello Yogesh,
When you say the impurities have been checked, would that be metallic impurities only? As you may know basic analysis will give you bath constituents, and 3 or 4 metallic impurities such as copper, lead and zinc. Organic impurities are normally not analyzed in routine bath analysis. When was the last time the bath was carbon treated? The last shop I worked for we would carbon treat when the bath turned a dark green color. Leave a bath sample of the untreated bath aside, then draw another sample after 4-6 hours of carbon treatment. The treated beaker sample should produce a clean emerald green color that is fairly translucent. You will notice a big difference in the color and clarity. Our supplier nor independent labs we worked with could not give us organic impurity levels because they were not set up for it. The second possible cause I would investigate would be the wetting agent concentration. If you do carbon treat consult your supplier so they can advise you of any additions to be made before you begin plating. The carbon treatment can pull out important organic ingredients. Hope this helps.

[But] I have to say I am totally confused with your post. You state you are getting the whitish haze after nickel and chrome, same effect under the nickel and chrome, and also after nickel plate. Where are you actually seeing the haze?

  Hi Yogesh. You did indeed post pictures, but I think the problem Mark references is that but your postings seemed to imply that this whitish look was present earlier in the process, possibly before any plating, or possibly after nickel plating but before chrome plating.

Can we call that a misunderstanding, say that the pictures are all after chrome plating, and that you do not have evidence of any whitish look until the wrenches are chrome plated?

Regards,