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Yellow shade in decorative chrome plating

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Q. I have a Nickel-chrome project with an Aluminum (Al-6063) base, I've been requested that the Nickel-chrome must achieve a white reflection. But my end product had a slight hint yellow / bronze reflection.

Because it is an aluminum base, I go through a traditional EN process with double zincate to the desired plating thickness (15 microns) followed by Cr (between 0.2 - 0.5 microns)

From the base material, we did perform aluminum chemical polishing for matte and gloss, mechanical polishing with different grades of sandpaper (500,1000,3000). But both polishing methods did not achieve the desired end product color, as long as the product enters the EN process it will end up yellow/bronze.

(We also tried Bright EN, and semi-bright EN, it also didn't work, because as far as my understanding goes, the base color of Nickel by itself is already yellowish/bronze.)

With these steps I'm not able to achieve the requested white reflection as I have noticed a slight hint of yellow as mentioned above, may I ask do we have any methods to change the Nickel reflection from yellowish/bronze to white?

Freddrick Lim
- Kuala Terengganu, Malaysia
September 8, 2023


A. Hi Freddrick. Chrome plating is considered blue-white compared to the yellow-white of nickel plating. It should not be deposited directly onto electroless nickel but onto bright nickel.

May we ask how you know you have 0.2 to 0.5 microns of chrome on the parts?

Is it possible that you are calculating this thickness based on immersion time rather than actually measuring it? Something important to remember is that chrome will not deposit at all if the current density is too low.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




⇩ Related postings, oldest first ⇩



Is chrome plating clear/transparent?


Tip: People don't like to give and not receive. Readers often reply to actual situations (from which they can learn), but less commonly to abstract questions.

Q. I've read your chrome information and I not completely clear if chrome is just a blueish, hard, clear coating and that the silver is just the polished nickel underneath. If you chrome plated copper, would it be shiny copper colored?

Peter Felice
- Chicago
2006


A. We misspoke if we said or implied that chrome is clear. It is not; it is metallic in color. It is a very slightly blueish white metallic color, but definitely metallic rather than blue. The color difference between the very slightly yellowish color of nickel and the very slightly blueish color of chrome and the whitish color of silver is subtle, but becomes obvious when parts are next to each other in good light.

Copper is often "hard chrome" plated, which means a very heavy coating of chrome; and in this case the article looks a lot like bright cold finished steel. In decorative chromium plating the thickness is usually inconsistent, and if a very thin coating of chrome, 10-20 millionths of an inch, typical of decorative nickel-chrome plating, were put directly onto copper it would probably just look discolored and crummy because the copper might partially show through in some areas and not in others.

Please help us help you by telling us what your actual situation is, so we don't have to answer with ifs-ands-&-buts which may still miss the heart of your issue. Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006




Nickel plating on restored modern furniture

Q. I am interested in learning more about options for specifications and industries capable of producing plated metal finishes on steel (and spring steel) furniture components. This furniture is completely disassembled, has been cleaned to bare metal (but not sand-blasted, acid dipped or pickled) and has a variety of shapes and sizes (largest piece probably about 28 inch dimension). I am interested in the warm silver tones that nickel seems to provide when included in the plating alloy, but I know little about the chemical formulation of other metals used for this effect on these types of steel components - - - are they copper, chromium, zinc?

Also, I know little about the different characteristics between electroless plating and electrically charged dipped plating.

Can someone help educate me about the options, and also direct me to reputable and experienced plating companies in the Boston region?

Thanks much.

Robert Arthur
architect - Cambridge, Massachusetts
2007


A. Most bright work for the last many decades has been nickel-chrome plated, Robert. Look at trucks or Harleys for an example of this. This finish is produced by nickel plating and then adding a very thin topcoat of chromium plating. The chromium is valuable for resisting corrosion in this difficult exterior service, and the chrome deters the nickel from tarnishing while it adds a bluish cast.

If the chrome is omitted (which is probably okay for interior service, less okay for tough exposures), the color is more yellowish -- indeed warmer. We are not talking gold or brass color, just a faint cast to the metallic look. Practioners may describe silver as "whitish", nickel as "yellowish" , and chrome as "bluish". Nickel tarnishes (it grows yellower over time if the tarnish is not polished away). Times change and public tastes change, but nickel is "in" these days.

Although electrodepositing alloys like brass is possible, and various tints are possible in gold plating, in general the color of electroplating is not controlled by alloying; rather the item is either nickel, chrome, or silver colored.

Electroless plating is, in general, much costlier than electroplating and applied only for its functional properties, not its decorative value.

This site is possible through the support of a number of plating shops, including some in your area, which you can see in our Directory of Jobshops. We can't also ask them to bear the cost of posting testimonials to their competitors who pay nothing, so we can't print recommendations of specific shops here. Good luck.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


A. If you are looking for warm silver tones you might be looking as Ted said for nickel + chrome. If you are looking for silverish finish nickel alone can provide it, most shops today can plate a very white nickel. It is necessary to top coat the nickel with either lacquer or clear powder coat. Other finishes popular with the furniture and hardware manufacturers are satin nickel (has a stainless steel type look), brushed nickel (similar to satin but with "brush marks") various "antiqued" nickel and brass colorations, etc. I suggest you talk to someone in you area who specializes in refinishing.

Gene Packman
process supplier - Great Neck, New York




Q. I am doing decorative chrome plating.I am facing the problem of yellowish shade at low current area, but some time this yellowing spread so much that rejects the piece. Can anyone help me to tell what could be the possible reason of this yellow shade in low current area?

Umair Khan
plating shop employee - Lahore, Pakistan
December 7, 2010



simultaneous replies

A. Not enough plating time is a good starting point. Next, you need to look at auxiliary anodes that face the low current density areas.
You have said "zero" about your tank setup. How can anybody do anything but guess at what the real problem(s) might be.

James Watts
- Navarre, Florida


A. Umair, Hi.
Your catalyst, sulfuric acid is too high. Slowly reduce to the right level.Chromic Acid to Sulfuric acid ratio should be 100 : 1.

1) You can add barium carbonate to reduce H2SO4 content or
2) Alternatively, slowly increase your Chromic Acid content.
Good Luck.

SK Cheah
- Penang/Malaysia


A. It sounds like simply poor coverage showing nickel as the yellow colour.
This will mean you have too high a catalyst most likely too high sulphate.
If you have no accurate analysis of sulphate, start adding barium carbonate in small amounts with good stirring.
Assuming you get improvement in coverage keep adding until you get some iridescence in low CD which means you have gone too far so just add the equivalent amount of sulfuric acid to remove the iridescence. You now have the correct CrO3/SO4 ratio for your bath. Take a sample and have it analysed and maintain that ratio. Some baths work at 100:1 but most work at a variation of this and you need to find your optimum ratio.
2 Kg of BaCO3 will remove 1 kg of H2SO4 equivalent to 555 ml of H2SO4 1.84 or 98%

Geoffrey Whitelaw
Geoffrey Whitelaw
- Port Melbourne, Australia


Q. How much is sulphate reduced by 1 kg of barium carbonate?

Adesh Sharma
Plating officer - Noida, India
February 3, 2011


A. Hi, Adesh. It seems you didn't quite understand Geoff's response: 1 kg of barium carbonate will remove 1/2 kg of H2SO4.

Good luck!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey





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