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Uniform Thickness of Hard Chrome Plating

We are doing hard chrome plating on baskets which are used in paper mills. We are not getting uniform thickness of plating inside the groove. The groove is of 'V' shape.The opening of the groove is 3 mm & depth of the groove is 1.5 mm. We are getting 200 microns thickness at the corner of the groove & 20 to 30 microns at the bottom of the 'V'. So suggest us what stapes we should take.

Jayesh s. Shah
plating shop - MUMBAI, Maharashtra, India
2004

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2004

You will never get a uniform coating with chrome. If you really need a uniform coating, investigate electroless nickel. If you can stand the cost, look at boron EN. I suspect that ordinary mid phos EN (heat treated)will outperform the chrome.

That said, you can help yourself by putting an appropriate chamfer on the top corner of the slot (both sides). This reduces the high current density area and provides a place for some of the excess chrome in the lessened high current density area to go. Using a conforming anode might help some, but I do not think that it would be worth the effort.

James Watts
- Navarre, Florida

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First of two simultaneous responses --

Your problem comes from electricity and its laws. All electrochemical processes present such variations, more or less pronounced depending on the type of chemistry and deposited metal. This is known as "throwing power". Highly acidic and inefficient baths have poor throwing power, while alkaline efficient ones are better. Unfortunately, hard chrome is the worst in high acidity and inefficiency. I agree with James, there are tricks like robbers and auxiliary anodes, but no trick will produce perfect results. Electroless Nickel (no electricity), though not perfect nor totally equivalent to chrome might be your choice.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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Second of two simultaneous responses --

Jayesh bhai

Chrome does not have very good LCD throw. Contact a good jig maker and have an auxiliary anode designed for this application. It will help even out deposit distribution.

Look at Electroless Nickel which has 12 percent phosphorus as the alternative. It can be heat treated to 1000 Vickers. The coating is very uniform all over.

Regards

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016
2004

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Jayesh,

I'm agree with all answer but electroless nickel would not help you if you not circulate the solution so you get a exchange by the nickel solution.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2004

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Anders,

No competent EN plater would fail to use adequate agitation of the fluid. Air agitation is a requirement for some EN solutions or you will be replacing the tank after a very few turn overs.

James Watts
- Navarre, Florida
2004

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James,

Yes I know but air agitation is not good enough to get the uniform thickness all over the area especially there you have small holes. It's necessary to use a pump to exchange the solution horizontal or vertical.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2004