Spotting problem in nickel-chrome plating

"Nickel and Chromium Plating"
by Dennis & Such

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A. Hello, Aurobind. It is hard to guess whether you have algae in your rinsewater. But a final rinse in DI water is pretty much a standard idea for decorative chrome. Is your final rinse DI water, and if it is not, is there a reason it can't be?

A. Although molds and algaes can grow in plating rinse waters I am not personally familiar with them in chromium rinses, possibly because of the oxidizing potential and toxicity of chrome. If you are able to photograph the stains in question, perhaps some of our readers who are experienced chrome platers will volunteer their opinions.

A. You may have a problem trapping gas bubbles during nickel activation prior to chrome. If so, you either need more amps, or some agitation. Under the bubble, if it is not released is unactivated nickel, which means you are more than likely white washing.
Also, check your ratio.

A. Dear

I have seen algae and spots due to it. One can see it under microscope very well. We started cleaning our storage tanks regularly and we installed 5 micron filters in DM line which solved problem. ( somewhere we had installed UV lamps around pipe too ) Regular cleaning of tank (preferably tank with tiles and not plastic tank ) was better.

Also measure silicate in DM water. It can also cause spot. keep level of silicate < 1 ppm.

Good luck.

"Hard Chromium plating"
by Robert K. Guffie

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A. The phrase "hard chrome" usually implies a certain thickness of the chrome deposit rather than a minimum hardness, Aurobind. Thicknesses that are measured in ten-thousandths of an inch or thousandths of an inch are called hard chrome, whereas thicknesses measured in millionths of an inch would not be considered hard chrome. Unless I am confused you are speaking of decorative chrome on top of duplex nickel.

This reason I mention it is because it would be hard to see peeling if the layer is only millionths of an inch thick. The question is at what layer the peeling is occurring -- between the two nickel layers, or from the substrate. You may be able to tell by applying a drop of copper sulphate ⇦this on eBay or Amazon [affil links] and seeing if it immersion deposits under the blister.

A. Dear Friend,
I have done nearly 7 years of nickel-chrome plating.
I have never seen or heard hard chrome plating on top of duplex nickel. What is your chrome thickness?

Second you need to dissect the problem. First you need to find out if the problem of peeling of is problem from the base(substrate)to nickel layer or from the nickel layer to the chrome layer.
There could be many solutions depending upon the identification of problem.
You must examine the peeled of layer by flipping it both sides and under a microscope to determine, where it is coming from...

If it is from Base to nickel layer:
Make sure the base is cleaned properly, rinses are good,lot of cleaning with good agitation...
If it is from nickel to nickel (semi bright to bright layer of nickel):
Make sure there are no sulfur based brighteners added in the semi bright tank. Check your filters...make sure they are crossed used between semi bright and bright nickel tanks.
If peeling from bright nickel to chrome layer...then make sure that you are not adding too much of brighteners in nickel bath. Activation of nickel layer is very important just before the chrome plating. All the rinses between nickel and chrome must be checked for purity,pH etc...too much time in air will passive nickel layer before chrome plating...too hot of nickel temp will passivate parts in air as well,...
Now finally Chrome plating itself must be good...check your rectifiers, make sure there is no tripping...
I can go on...but believe me peeling in nickel chrome plating is a very common problem and can easily be solved if you stick to the basics...
Best of luck..

Dear Kumar,

thank you for your valuable information.
I was suspecting whether peel of may arise due to additives and you have confirmed that. But chrome over duplex nickel is more predominant in India as most of the plating in shock absorbers are only of this type.

Regards

A. Good day Suresh.

It would appear your process is out of control.
If there is "SMUT"on the substrate and it is black, after acid dip, you cannot expect ANY measure of adhesion of the nickel. Is the "SMUT" on the entire piece, or only on the top/bottom? The blisters indicate HCD areas.
What is your acid dip, is it electrolytic?
What is the ASF in the nickel? What is the TOC value?
Come back with more info, cleaning process, acid dip, etc.
What is the substrate?
High stress in the nickel will compromise the columnar structure. What is it that you are analyzing for, and what are the values?
Maybe other readers can offer more insight, but more info is needed.

Regards,

A. Hi Suresh. Agreed, Eric.

It seems to me that if a component has smut on it, it would be expected to blister because you can't get proper adhesion to smut.

Regards,

Hi,

I going to try to explain for this letter and letter 44143, regarding bad adhesion and blistering when they chrome plate with nickel and chrome on a steel substrate.

The black smut you see if you use sulfuric acid as a pretreatment cannot give you a problem when you plate in the chrome. This smut is active smut. You must wait until the part is the same temperature as the chrome solution and let it start with a low current 0,5 volts up until the temperature is the same as the solution to reduce the oxide on the part.

To see the hydrogen bubbles before you increase the voltage slowly up to the plating range.