finishing.com logo
  HOMEFAQsBOOKSHelpWantedAdvertiseContactFORUM Letter 22456

The finishing.com Hotline -- Serious Education ... plus the most fun you can have in metal finishing

Bright dip process, copper parts brightening



An ongoing discussion from 2002 through 2015 . . .

(2002)

Q. We make copper tubular parts of 3/8" to 7/8" O.D. and Length from 1/2" to 1". My customer required parts to be bright & shiny and should remain bright for at least 6 months. Currently we clean it with detergent to remove oil and then acid clean and dip in brightener. They come out good. But when it reaches customer they are tarnished. We tried to wrap them in VCI paper but did not help. I will appreciate any help in this.

Thanks.

Regards,

Gautam C. Patel
- Ahmedabad, Gujarat, India


(2002)

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 :-)

SONGYUTH PANYAJARAY
- Bangkok, Thailand


(2002)

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.


AF Kenton
Nova Finishing Sytems Inc. - Hatboro, Pennsylvania


(2002)

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

Jon Quirt
- Minneapolis, Minnesota

wikipedia
Imidazole

Covalent Bond


(2002)

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.

Viney Chaddha
- Gurgaon, India



To minimize searching and thrashing, and to provide multiple points of view, Finishing.com combined formerly separate threads into the single dialog you are now viewing. Please forgive any resultant repetition.



(2003)

Q. Could someone please explain the Bright Dip process for copper to me. Are there chemicals involved?

Vickey Lopez
- Deer Park, New York, USA


(2003)

A. Hi, Vickey,

In principle, bright dipping is a process where an oxidizing acid like nitric acid or sulphuric 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 :-)

Ted Mooney   Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2003)

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

v k thomas
- bangalore,karnataka, India


(2003)

! 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.

Ted Mooney, finishing.com   Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2003)

Dear sir

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

thomas v k
- bangalore karnataka, India


(2003)

thumbsup2Thanks Thomas. Now your response sounds good! Thank you.

Ted Mooney, finishing.com   Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Cleaning ID of copper waveguide

September 2, 2008

Q. I work at a small R&D company that is currently doing work on a particle accelerator. We make our own waveguide (WR62) components since most of what we do requires unique assemblies. All of our parts have flanges brazed onto them, and subsequently are left with a hefty layer of scale/oxide. Normally, we just have a local job-shop clean them, presumably with an alkaline dip. However, in order to improve the turn around time on these parts, I am trying to find a way for us to get the ID clean in-house. Ideally, it wouldn't require much in the way of special equipment or handling beyond the capabilities of a basic laboratory. So far, my best approach would be to use Hydrochloric acid to etch off the scale, but I don't know if that would be effective on really heavy scale.

Can anyone recommend a particular method that would work for our needs?

Josiah Hartzell
Researcher - L.A, California, USA


September 3, 2008

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.

harry_parkes
Harry Parkes
- Birmingham, UK



April 13, 2012

Q. I silvered brazed some copper tubing to brass plates, then silvered brazed some 316 ss blocks to it, and soldered 96/4 some copper lines to the side. Sent the parts off to bright dip and the silver braze joints had a black film on them when I got them back, any clues why? Edgar

Edgar Babineau
metal fab. - Merrimack, New Hampshire



Best chemical solution to clean copper after machining with minimal etching?

May 19, 2015

Q. We need to clean copper of tarnish and dirt left behind after machining the part.

It is critical that we maintain the current dimensions of the part, so only very minimal etching is allowed.

I have tried dipping a test piece in diluted nitric acid and it does clean the part.
But what is the etch rate of nitric acid?

Is there a better chemical for this application?

Randy Thelen
Chemist - Salt Lake City, Utah, USA
  ^- Privately contact this inquirer -^


May 2015

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/sulphuric acid tarnish removal and brightening step. Good luck.

Regards,

pic of Ted Mooney   Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 20, 2015

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 persulfate (50 g/l) or ammonium biflouride.
Please see letters 51199 & 45635.
Hope this helps.

Regards,

Eric Bogner
Lab Tech. - Whitby, On, Canada

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It is not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & DevicesUsed & Surplus


©1995-2015 finishing.com     -    Privacy    -    Search