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topic 4076

Brass plating is too yellow, need gold color


(1999)

We do Nickel/Brass Plating in an automatic barrel line.

The color of our brass is lemon/yellow.

Our customer wants a golden color brass.

Any suggestions on chemical composition to achieve a golden color brass.

Ed Esposito
- jersey city, New Jersey


(1999)

Good Morning,

Many years ago I ran bright brass to look like a gold finish. Cyanide copper / bright nickel [must be bright] to brass plate, just a flash over, with a "sealer" style dip afterwards ... finish very close to gold.

Hope this helps ,

Ron Landrette
plating equipment supplier - Bristol, Connecticut


(1999)

Dear Mr.Esposito,

After a long experience, I learned that the lemon/yellow brass bath is one of the most stable brass baths, except perhaps of the "white brass" solutions. Any attempt to modify this standard color of the deposit, by changing the concentration of some constituents, will result in unstable colors of the coating and many head aches. For automatic production there is no other solution. If your customer wants another tint of the deposit, you may choose between light bronze coloring ( antiquing )the deposit or applying a colored transparent solvent lacquer.

Depending of the nature of the plated objects, I think that the alternative to apply a very thin (0.06 - 0.08 µm ) layer of gold from an acid gold-cobalt bath, after nickel plating, is not be neglected. Apparently this is more expensive, but if you put in balance the cost of frequent analysis of the brass bath ,of the passivation and lacquering of the deposit and of the destruction of cyanides,gold plating may be the best treatment- for which you may also ask a better payment.

Best regards,

Emmanuel Popesco
- France


October 2, 2012

I wouldn't recommend trying to change a stable bath to satisfy one customer. You will be fighting a losing battle with all other comers. It wasn't mentioned whether you lacquer the parts or not and if they are baked after lacquer. I have turned bright brass a gold color by baking them at 285 °F for approximately 20 minutes. This will work with a "flash" deposit. If you must change your chemistry, I would recommend a 4:1 ratio of Zinc metal to copper and a 4:1 ratio of Zinc metal to free cyanide and run it at a slightly lower current density to draw out more copper. Hope this helps.

Bruce Wheeler, Finishing Engineer
- Berlin, Connecticut USA



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