Chrome-free Alternatives for Bright Dip of Copper and Brass

A. Rey - Try using a peroxide based bright dip. These are generally 10% or so sulfuric and the rest water and peroxide. This will produce a beautiful finish on copper, brass, etc., without the nitric cloud. As an added bonus, if you're only processing copper, the major waste byproduct is copper sulfate - something you may be able to sell to a chemical mfgr. in your area.

Q. I already tried and tested peroxide based bright dips from four different suppliers. Peroxide based bright dips works well with brass which leaves a shiny finish but leaves white spots on our parts surface if inspected under microscope.

Peroxide based bright dips do not perform well on beryllium copper and phosphorus bronze alloys. Hydrogen peroxide also upsets our chemical treatment. It reacts with dissolved non-ferrous metals by foaming a lot in the chemical treatment. I looking for a bright dip that does not etch non-ferrous alloys.

A. Rey, you could be absolutely right that sulfuric-peroxide is not a good choice for your circumstances, and you may be right to dismiss it in your particular case. But for other readers, and the more general case, I do know of shops that successfully bright dip beryllium copper with sulfuric-peroxide; they do solvent drying, rather than water rinsing & drying, and you might want to double check that the white spots are not salt residues from water rinsing.

The next person shouldn't necessarily write off sulfuric-peroxide--I think it may be worthy of a careful second look. Best of luck!

A. Is this a live enquiry? We still supply Zenith Cub.

A. Here we do Bright dipping of copper Terminals which are used in Automotive batteries.
The Process Flow is as below:
1. Cleaning : By means of Kerosene and Saw Dust
2. Rinse : Rinse the material by means of Raw Water
3. Solution Make Up: Ratio of 4:1:1 (4 Parts of DM Water : 1 Part of Nitric acid & 1 Part of Sulphuric acid all are commercial grade chemicals). Dip in the same for few seconds as the copper will melt in the solution its just a surface preparation for the adhesion of PASSIVATION.
4: Rinse : Raw water Rinse Twice
5: Passivation : Yellow color as per you are requirement
6: Rinse : Raw Water Dipping once
7: Drying : any type of Dryer can be used

Regards,

A. Mr Mosley

It is unlikely health data sheets disclose the full monty .

There are good companies all over that make brass bright dips.

If you wish, we can send help -- some proverbial coals to Newcastle from Delhi.

Regards

Mr Nurie

Thanks for your response however, I have now solved the problem. The 'recipe' from the data sheets is based on using concentrated acids. The solution I have at the moment has been made up, % volume, using commercial acids at around 60% concentration. Hence the reduced activity. With an accelerator the solution works fine.

I have indeed found numerous companies who produce bright dips but the newer products tend to run at elevated temperatures and have different effluent treatment requirements.

Again many thanks for your response.

Hi Richard, glad you solved it. Sometimes higher temperatures help to solve treatment and waste issues. For example, the sulphuric-peroxide may operate at a high temperature where the solubility of copper is high, so that it can be cooled to precipitate out the copper sulphate for recovery rather than needing treatment.

Regards,