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topic 36277

Hard Chrome plating with Nickel undercoat



A discussion started in 2005 but continuing through 2018

(2005)

Q. Dear Sir/Madam,

I would like to increase the corrosive resistance of Hard-Cr plating over steel substrate by doing an undercoat of Nickel. However, no matter with electrical Ni plating or electroless Ni plating undercoat, the hard-Cr layer did not adhere well and peel off easily. Is there any way to improve the adhesion of Hard-Cr over Nickel coated substrates?

Thanks.

Norman Chow
plating shop - Hong Kong


(2005)

A. From my experience time is a critical factor in obtaining satisfactory adhesion. Nickel passivates rapidly and once passive does not make a good substrate to plate on.

We have worked on a maximum transfer time from Nickel plate to Chrome plating of two minutes (including the rinse between stages). This has given us sufficient adhesion that we are able to grind after plating without flaking.

If you cannot transfer between the Nickel and the Chrome within that time then you will need to look at a re-activation stage immediately prior to immersion in the Chrome bath. I have seen both Hydrochloric and Nitric based activators used for this purpose.

Brian Terry
Aerospace - Yeovil, Somerset, UK


(2005)

A. Activation with acid salt, and water rinse, and activate in chromium plating bath with about 2 A/dm2 for about 5 min, and the increase the current step by step about 5 A/dm2 per minute.till 150% of normal current stay at that for 3 min and then return to normal current.

Bryan Chen
- Hefei, Anhui, China


(2005)

A. Norman,
I will recommend a nickel layer without any brightener you can use a sulphamate nickel deposit. To get a good adhesion on a part is always to use right pretreatments before plating. Search here at finishing.com letters on activation.

Regards,

anders sundman
Anders Sundman
3rd Generation in Plating
Consultant - Arvika, Sweden



(2005)

A. Dear Mr.Chow,
In India people are doing hard chrome on duplex nickel for automobile shocker by doing this they are getting properties of hard chrome & corrosion resistance of nickel.
But in preline we need sulphuric acid etching before going for nickel.

vishwas nangare
Vishwas Nangare
motorcycle accessories mfgr.
- Aurangabad, Maharashtra, India



Hard chrome hole edge has a yellow color

January 29, 2018

Q. We are struggling with a copper part that is to take a nickel, hard chrome layer. The part would be plated very well except for one of the holes. The edge of the hole would have a very thin yellow edge that is unaccepted by the customer and we are struggling to fix it. We tried changed CD and amount of additives but nothing happens.

Ahmed El kady
- Cairo, Egypt

January 29, 2018

A. Typical, The gas evolution from the hole is displacing solution from around the hole and preventing chromium deposition.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como



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