Bright dip process, copper parts brightening

A. Here in our company, we also have parts made from copper also, and our customers do want to keep it maximum 1 month (I know that's less that your specification).

We have two choices: First way is keeping treated parts in an aluminum bag with vacuum, it takes very high cost but nearly 99% foolproof. In our company we choose to keep these copper treated parts in the normal Plastic bag (thickness over 0.8 mm) with nitrogen Gas atmosphere and Desi Pak (moisture absorber), and this was recommended by our customer from Japan to allow lower cost and still be effective. Parts can be kept around 1.5-2 months without any oxidation happening.

And the second way, is to do chemical dip; after you do acid dip and brightener dip, try to dip with Chromic acid 10 g/L maximum . It can protect against tarnish but I'm not sure that it matches with your process or not and how long can parts be kept.

Please note that the important method to keep Copper parts in good appearance is the way to pack, not the way to treat :-)

A. There are at least two ways to brighten parts using mass finishing systems. One wet, one dry. You can steel ball burnish parts and then do your cleaning process and suggested packaging. Alternate way may be less expensive is to use treated dry organic materials, blow off, and then just package. This dry organic process will leave a fine film on parts and if they are not touched by bare hands, they will maintain their appearance for at least a month, plus. It depends on the dry organic additive in the mix.

A. Immerse in Imidizol, Like a new penny, This forms a covalent bond with the copper, no 02 available to react.

A. Dear Gautam,

After brightening you can chromate them. In fact for chromating them using proper chemical. I had got the results you desire. You can contact a representative and he would help you out in chromating. For brightening it I had used electropolishing in phosphoric acid.

A. Hi, Vickey,

In principle, bright dipping is a process where an oxidizing acid like nitric acid or sulfuric acid plus peroxide smooths the surface of the copper to make it more reflective. Depending on the acid used for smoothing, a followup acid dip may be needed to remove the oxide it generates.

Please describe your situation though. We don't know if you are a consumer trying to brighten a single copper-bottom saucepan, or an engineer inquiring about what is involved in building a factory to automatically bright dip a thousand pieces an hour :-)

A. Dear sir
Try the mixture of H2SO4 20% and NaOH^^HNO3 20% and 60% of water. This mixture will remove the oxide on the copper, then dip in the hydrochloric acid; this will remove the smut on the part okay

! Maybe there is a typo in your response, Mr. Thomas? I don't see how mixing an acid with an alkali will result in anything but salty water. I would expect it to remove tarnish, but I wouldn't expect any real brightening unless I'm missing something.

Dear sir

I am very sorry to type HNO3 as NaOH this mixture will give a bright finish to the part.

Thanks Thomas. Now your response sounds good! Thank you.

A. Hi,

Suggest the following sequence:

1) If there is any flux on or around the brazed joints remove this first. Very hot water is effective with many fluxes. If your parts will withstand the thermal shock, put them in the water while they are still hot.

2) Remove the black oxide in 10% v/v sulfuric acid at 60 °C (140 °F).

3) Chemically brighten in 80-85% phosphoric acid containing 6% v/v nitric acid. The concentration of nitric acid is based on using 60% w/w. Operating temperature not critical - room temp is fine. Some brown fume (nitrogen dioxide) is evolved so use in a well ventilated area. If you are not happy with that, consider sulfuric acid / hydrogen peroxide based brighteners.

Rinse throughly between each stage.

A. Hi Randy. Cleaning off "dirt" is a different thing than removing tarnish: strong hot alkalines will remove dirt very effectively, and they can do it with no etching, but they won't remove tarnish or brighten the copper. Pending input from other readers, please consider a hot alkaline cleaning step followed by a peroxide/sulfuric acid tarnish removal and brightening step. Good luck.

Regards,

A. Good day Randy.

Ted offers some advice on cleaning the "dirt/soils" with alkaline cleaners. You can also try reverse alkaline cleaning (the work piece is positively charged) and to remove the tarnish, you can use 10% sulfuric acid with ammonium persulphate (50 g/l) or ammonium bifluoride.
Please see letters 51199 & 45635.
Hope this helps.

Regards,

A. Hi David. I'm guessing that you are doing a very small volume and are hand cleaning assemblies rather than doing lengths of copper tubing?

If the volume is high, and you are doing copper tubes rather than assemblies, a proper brite-dipping line would probably be an improvement and might include alkaline cleaning, a dip in proprietary sulfuric acid / hydrogen peroxide, and then a dip in diluted sodium benzotriazole ⇦this on eBay or Amazon [affil links] (with rinsing between each process).

Regards,

A. Hi Danny. I'm not really understanding your question; you might want to reword it ... but certainly a bright dipping line can handle mass production.

Luck & Regards,