HARD CHROME PLATING TROUBLESHOOTING

A. HI TOM

I would mention two things which other have not mentioned here, may be they will be helpful to you to avoid haze. Try 2-5 grams per liter of chromic acid pre dip just before the chrome plating bath.

Second, try to see if your water rinses after (if you nickel plate) nickel plate are too cold. If so, try a bit warmer water in these rinses. Hope it will work. Nice to see responses here from as far as India. I think I know Mr. Varun Bhalla ... World is shrinking, is not it?   :-)

A. Many of the other replies are suggesting the problem as passive nickel which generally gives a strong stainy haze. A very light haze can come from high fluoride in the chrome bath, common in some of the earlier SRHS baths.

A. I don't have your haze problem, but if your chromium activation solution is too old (I mean the conductivity is too little) in the low current density areas you can see some hazy deposits.

A. Hi Tom,
There are many reasons for haze.
As I have observed, temperature plays an important role. After that the ratio and amount of sulphate -- if the sulphate ratio is low then haze starts for chrome plating which does not get clear during buffing. We lastly observe the current -- sudden supply of current creates haze during chrome plating.

A. Tom,

if parts come out cloudy after chrome plate, check chrome ratio, check the nickel brightener is not loaded too much, fallen parts in nickel or chrome tank touching with your plating rack parts. Other possibility passivation nickel surface.

"Hard Chromium plating"
by Robert K. Guffie

on AbeBooks
(rarely)

or eBay
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A. The answers to 1 and 2 will fill a book.
For better adhesion, you add nothing! you do a better job in the prep steps and maintain your chrome tank within specifications.
Hard chrome is very bright if the substrate is smooth and if you are using the correct amperage per square inch for the temperature of the solution. There is a window that is bright and outside of that it is burned or cloudy or milky. PS it is not "hard chrome" if it any of those. It will be much softer!
You would be well off to buy a book that is listed at this site's book list.

A. Dear sir,
The problem may be with improper cleaning.Review cleaning methods and check degreasing solutions to make sure that they are efficient.And check the operating temperature, at 55-60 °C temp it works better.The chromic acid concentration should be at 250 gms/ltr and sulphates 1.8-2.25 gms/ltr.

I don't claim I understand, but Lowenheim [on AbeBooks, eBay, or Amazon affil links] has a good chapter. Let me at least try to help this gentleman in India from book experience and from theses and papers:

Problems:
1/ poor throwing power, plates more on ends and edges.
2/ cracks in the plating.
advantages:
1/ adhesion is automatic from chromic cleaning
2/ easy to maintain bath
hazards:
1/ formation of oxygen AND hydrogen gas bubbles.
2/ carcinogen

Anode issues:
1/ chromating like sulphating of battery and needs cleaning of Pb anodes. solution: use 10% silver anode.

I hope someone can add more.

The ratio of catalyst is very important. The temperature control is very important. If you have XRD, you can follow the crystal structure.

A. Hi Elham,

Possible causes are:

1. Too high pH (>3).
2. Too high plating solution surface tension (low wetting agent).
3. Too low chromium concentration.
4. Metallic impurities (e.g., Zn, Pb).
5. Poor nickel activation prior chromium plating.
6. Plating part dries off prior chromium plating.

Regards,
David

A. I'll add two other possible causes of problems: catalyst too high/low, and chloride contamination. The latter is common in shops that try to cheap out on the rinse following the nickel plating step. There is no way, that I know of, to remove it.

The former problem can be evaluated via Hull Cell or chemical analysis for sulphate and/or fluoride.

A. Silver nitrate will precipitate and remove chloride from chrome plating solutions.

A. Hi Elham. Letter 56140 "Determining and removing chloride in Chrome plating solution" describes a method to dummy it out at high temperature and high current density.

Regards,

A. I would like to add one more item to the excellent answers have received so far. Any parts on the bottom of the plating tank can also cause this problem.

A. If the bath chemistry is correct, milky deposit is almost always by too low a current density for the temperature of the solution.

Hi. Thanks for suggestions especially David Shiu. I used your suggestion and corrected the chrome tank.

A. Hi David. Unfortunately, you must send them back to the same or a different plating shop for replating. There is no way to repair the missing chrome.

Regards,

A. May be due to low sulphate or low temperature.

A. Hi David,

You have to strip the chrome, and plug all holes on part, and rechrome all parts. Strip chrome - rinse - activate Ni surface - chrome predip - then chrome the parts (and check your chrome tank chemistry).

A. The most common cause of cloudy chrome plate is the wrong current density for the bath. Assuming a common chrome/sulphate bath, then the temperature is probably too low for the current density applied.

"The Canning Handbook of Surface Finishing Technology"

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Amazon

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A. Hi cousin Prabh. The Canning Handbook lists the number one cause of little or no chrome deposit as nickel plating which has grown passive. The same handbook suggests the number one reason for adding barium carbonate is to correct poor throwing power.

Unfortunately, we probably need much more data to guide you through.

Are you an experienced chrome plater and this new problem appeared on parts you previously plated successfully? Was it sudden or gradual? What was the ratio before and after your barium carbonate additions. Is this a new part, perhaps requiring greater throwing power? Details please! Thanks!

Regards,