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Need to know the basics of 3rd layer of nickel plating

Q. We are using a chemical additive for the last (third) layer of nickel plating, the supplier from Taiwan said to us it's micro nickel but in fact there's no micro powder for this tank. The solution just contains nickel chloride & two additives. I think this kind of solution is just for improvement of chrome plating ability -- but not 100% sure. The supplier will stop to provide this solution to us in the next two months and we have to look for local suppliers, but no one knows what kind of that solution is. Can anyone can supply or tell me the basic of this solution? Thanks!

Nguyen Ngoc
Plating shop - Nam Dinh, Vietnam
2007

A. Hi Mr Nguyen,

Your 3rd nickel layer is generally called micro-porous nickel. It is used for improving the corrosion protection of plated parts, not for improving the chrome plating acceptability. The first nickel layer is semi-bright nickel, which is contributed about 2/3 of total nickel thickness. The second nickel layer is bright nickel, which is contributed about 1/3 of total nickel thickness. The last nickel layer is micro-porous nickel, which is very thin layer, probably less than 50 micro-inch thick. Chrome is then plated over this tri-layer of nickel.

The micro-porous nickel solution has to contain micro particles, otherwise it is not called micro-porous nickel. The micro-porous particles could be in white fine powder form, which has to dissolve in DI water before adding to nickel solution. The micro-porous particles could also supplied in the white slurry solution, which has to mix well before adding to nickel solution.

Contact Enthone (Cookson Electronic) or Atotech if they have regional office in Vietnam, China, or Southeast Asia for the chemical that you are looking for. I used their products before.

Hope it may help you.

Han Nguyen
- Chicago, Illinois, USA
2007

Increase chrome plating pore count with fluoride catalyst?

Q. Does the fluoride catalyst directly effect the amount of pores in the deposit?
I'm looking to increase the amount of pores without using particle nickel.
Any thoughts?
Thank you

Troy Sicilia
- Vancouver, Washington
March 13, 2014

TUTORIAL FOR NEWBIES:

Decorative chrome plating is actually one or more layers of nickel plating followed by a very thin final layer of chrome plating. That is because the leveling, reflectivity, and a large measure of the corrosion resistance come from the nickel plating.

Nickel-chrome plating must be exceptionally well done or it is much worse than nothing at all because steel is anodic to nickel, and if the plating is porous, cracked, or pinholed it will greatly accelerate the rusting of the underlying steel. Just as zinc anodes dissolve preferentially to steel and can be used to protect it from rusting, steel dissolves preferentially to nickel and will rapidly rust through those pinholes to try to protect the nickel.

A common strategy to improve the corrosion resistance of nickel-chrome plating is to apply two layers of nickel, i.e., semi-bright nickel followed by bright nickel; this is called duplex nickel plating. The bright nickel is anodic to the semi-bright nickel plating so the corrosive forces tend to spread laterally, dissolving the bright nickel, in preference to penetrating through the semi-bright nickel and reaching the steel. Our FAQ, "Introduction to Chrome Plating" covers these and other issues and includes photographs.

The chrome plating generally has cracks or pores, and an additional corrosion fighting mechanism is to try to fill the chrome plating with millions of small pores, rather than a small number of large ones, to try to distribute the corrosive power across the whole surface rather than concentrating it. One of several ways to try to increase this microporosity is to apply a 3rd layer of nickel which is designed to encourage porosity in the chrome plating.

A. If you want a porous deposit you have to use micro-porous Ni. There is a possibility to use a post-nickel strike for a micro-cracked deposit, which is chloride based nickel bath, working at low temperature (max 30 °C) and higher current density. Fluoride catalyst from hex-chrome does not have any influence in pore/crack count.
Keep in mind that you have to use a hot rinse (60 °C) when using a micro-cracked Ni, after chrome plating.

Vlad Manta
- Oradea, Romania
April 4, 2014

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