Copper Wire Cleaning, Oxidation Prevention, Lacquering

A. Please check what type of plastic reel you are using. Any plastic or cardboard that contains a moderate level of sulfur can outgas and accelerate the tarnishing.

A. Hi Matthew. There are several different types of "bright dips" for copper. Some are based on nitric acid, some on sulfuric acid plus hydrogen peroxide; some are based on other oxidizing agents like persulphate. But the thing is, you don't need to start with basic chemicals for this kind of task; you can buy a formulation. Proprietary suppliers will be happy to run samples for you and then help you bring it from their lab to your production line.

There may be no such grease or gel that will maintain a bright finish for years, but benoztriazole-based or chromate-based coatings will preserve the brightness for a while. Again, you can buy these as proprietaries, you don't have to invent and blend your own formulations. Talk to any plating supplier you find in our directories or in your yellow pages and tell them that you need a "bright dip" and a tarnish inhibitor for copper and they'll be pleased to give you workable processes. Good luck.

Incralac
(brass lacquer with benzotriazole)

on eBay or

Amazon

(affil links)

A. You can use Icralac ⇦this on eBay or Amazon [affil links] , special lacquer for copper and its alloys (Paraloid B 44 acrylic resin+ benzotriazole ⇦this on eBay or Amazon [affil links] as inhibitor, USA product). You can also use ORMOCER lacquer for copper and its alloys (heteropolysiloxane based, European product), if you can obtain it!

A. Benzotriazole, chromate coatings, and lacquers are three common approaches, Manhar. Search the site for more detail on these, or pose a more detailed question about them. Thanks.

Hi Viswanathan. The best anti-tarnish agent to add to your copper cleaner-polish might be Brasso ⇦this on eBay or Amazon [affil links] . The more you add, the better the tarnish resistance :-)

More seriously, there are dozens of successful existing commercial copper polishes. If you wish to manufacture your own version and compete against those brands, then reverse engineering an existing product, or searching for information about them in expired patents might be your easiest path. But there are formulations books available, and they seem to indicate that benzotriazole is common to almost all copper polishes. Good luck!

A. Hello Mark,

You could experiment offline first with Ammonium persulphate , using about 120 grams per liter or more ..for 10 to 12 seconds.

Hope this helps.

Q. Asif,

Will the Ammonium persulphate etch the copper surface? Thank you for the response. I am going to try that.

A. I've had good experience with citric acid ⇦this on eBay or Amazon [affil links] formulations when cleaning copper parts. Brightens them nicely, too. Contact Stellar Solutions [a finishing.com supporting advertiser] and they'll tell you all you'd want to know. 'Cept, maybe, about their competitors...

A. Ravish,
Perhaps dilute acetic or citric acid will suffice. Hopefully you will not have to resort to more potent processes because many stronger formulas or chemicals have drawbacks (reactions) when combined with copper.

Q. Dear sir, what may be the reason of pinhole in reference to bare portion, in other words how bare is responsible for occurring pinhole?

Hi Ravish. I think we're having some language difficulties, but even so, your postings are abstract, and it's hard to say much. How are you cleaning the wire before lacquering (Do you do alkaline cleaning or ultrasonic cleaning? Are you using the citric acid which was suggested?) How is the lacquer applied, and to what thickness? How is it cured? When do the pinholes appear? Do you draw the wire or buy it? Do you do the lacquering in-house?

I think your inquiry needs to be several paragraphs before anyone will be able to help you troubleshoot the issue. Good luck.

Regards,

Q. Dear sir thank you very much for your precious response. As I asked you reason for occurring pin hole on aluminium bare strip conductor. We produce bare from extrusion process. It does not occur in every lot. It is found in selected Bobbins. In some of the Bobbins it is found in large no. From starting to end of total quantity of bare conductor. We have both catalyst and conventional plant and this problem occurs at both the plants in selected lot it is found. I hope you will help me.

A. Hi. I'm sorry Ravish, but I get more confused with each posting. I thought we were talking about pinholes in the varnish on copper wire. But now we're talking about extruded strips of aluminum -- maybe they are "bars", maybe they are "bare" (devoid of coating). Where are these pinholes ... in some sort of coating on the aluminum or in the extrusions? Apologies but I have no idea what you are talking about. Are you talking about "bar conductors" and "bar copper wire" or "bare aluminum conductors (no coating)" and "bare copper wire"? Sorry.

Regards,

A. Hi Sajjan. We appended your inquiry to a thread where nitric acid or sulfuric acid + hydrogen peroxide or ammonium persulphate were raised as bright dip possibilities. It might be possible to do it with just citric acid or acetic acid ⇦this on eBay or Amazon [affil links] as Lee Gearhart and Blake Kneedler mention -- but those easier & safer chemicals are probably less capable.

After the bright dip, how long do you need it and expect it to stay bright? Without benzotriazole and a benign environment, or benzotriazole plus lacquer for a less benign environments, it may not stay bright for long. Good luck.

Regards,

Q. Hello Sir. Thank you so much for your guidance. Which acid -- nitric acid or sulfuric acid+hydrogen peroxide or ammonium persulphate -- is more effective?

Which one will give brightness in one process ?

A. Hi Sajjan. All have been used successfully for bright dipping copper. So have chromic acid mixes, but they should probably be avoided these days for environmental reasons. The sulfuric acid plus peroxide has environmental advantages, the biggest of which is probably that you can run it hot, and cool it to crystalize out the copper.

But in the USA and much of India, you don't formulate your own copper bright dips, you buy them from a plating chemical supplier. Please ask a supplier about their proprietary sulfuric+peroxide bright dip, which will probably contain stabilizers to deter premature breakdown of the peroxide. Good luck.

Regards,

A. Hi Ravi. Hi Parag...

Benzotriazole has been recommended 5 times on this page so far. What was the result when you tried it? If you have not tried it, please try to be clear on what your hesitation is, or what specific questions you have about it after inquiring of the plating suppliers. This is a public forum where we all learn from each other, and if readers are to have any expectation of help from others, they must contribute their own experiences. Thanks. Awaiting your reply.

Regards,

A. Hi Monojit. Per this paper from the Copper Development Association .
"The simplest way is to dip the metal part in a 0.25% aqueous solution of benzotriazole at 60 °C for 2 min."

But please read that paper in its entirely to better understand what we have already said on this page, that it is best to purchase a proprietary corrosion inhibitor formulation than straight benzotriazole; it's beneficial effects are amplified and its undesired side effects diminished through the addition of small amounts of other chemicals as discovered through proprietary research.

Regards,

A. Hi Arun. There are a great number of potential copper bright dips: from chromic acid to nitric acid to ammonium persulphate to sulfuric acid with hydrogen peroxide, and probably others. For short term tarnish prevention you can use imidazole or sodium benzotriazole. For longer term, and if conductivity is not required, you can use brass lacquer or other clear coats.

In case you don't know it though, these bright dips and tarnish preventers are available as proprietaries, and most shops buy and use proprietaries rather than having to hire chemists to develop their own formulas. It's hard to compete in 2018 using generic public domain formulas from the literature of 75 years ago :-)

Best of luck.

Regards,