Serious Education ... plus the most fun you can have in metal finishing.
Nitric acid substitute
Q. I'm looking for a chemical substitute for our nitric acid mixture bath used for chemical deburring of non-ferrous alloy electronic pin connector parts. Burr created during machining/slotting operations have to be removed chemically. Nitric acid mixture (30 - 40% nitric and balance is water) is used to etch down the parts by .001" in 15 to 40 seconds. Can anybody suggest a different chemical to do the same job. Thank you.Rey Tinio
- Yucaipa, California, USA
? What exactly is your problem with the nitric acid?
- Pearland, Texas
? What alloy are we talking about?Dan Weaver
- Toccoa, Georgia
Q. The problem with nitric acid is the requirement to install a scrubber. We want to avoid using the scrubber. Our environmental consultant told me that there exist numerous oxidizers capable of etching our beryllium copper, brass and phosphorus bronze parts just like the nitric acid.Rey Tinio [returning]
- Yucaipa, California
Well, there's life for ya. Your environmental consultant tells you nitric acid is a big environmental problem he can't solve, but finding a substitute should be like falling off a log. And the finishing people imply that finding substitutes would be a major problem, but your environmental guru should stop complaining about the trivial matter of dealing with nitric acid
I think the explanation is actually this: we live in an age of modern miracles, so we naturally tend to think of substitute chemistries as part of this modern miracle scene. But in most cases the reality is that the substitute technologies are really not new; rather, they are old technologies which were non-viable in the days before strong environmental and safety consciousness because the more widely used technology was simpler, less expensive, and more robust, forgiving, and versatile.
Elimination of nitric acid certainly can be done, but the new solution will probably be more expensive, less forgiving and less flexible. Which is to say: I'm pretty confident that you can etch that beryllium copper with a proprietary sulfuric acid - hydrogen peroxide etchant, but I'm not so sure you can do it in 15 to 40 seconds, and I'm not confident that you will be able to handle the brass and phosphorous bronze parts though the same system.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
A. Stabilized hydrogen peroxide with an acid could be used as with etching printed circuit copper. You would need to experiment with the best type of acid mix other than just sulphuric acid to give a clean finish.
- Port Melbourne, Victoria, Australia
A. I would add to the remarks that oxalic and sulfuric acid will titrate together in a simple acid-base titration, so your best bet is to determine oxalic acid with permanganate and then subtract it from your total acid result.
As for the acid-base titration: If the concentration of oxalic acid is high, you may be able to see a small inflection point between the first part of a potentiometric-end point titration curve - which includes all of the sulfuric acid and half of the oxalic acid - and the second part, which is due to just the second half (2nd proton) of the oxalic acid. You may be able to get better separation of the two parts by adding methanol or ethanol to your sample. I don't think an indicator method has any chance. A thermometric titration may work though (see my answer to letter 4626).Emanuel I. Cooper
I.B.M. - Yorktown Heights, New York
A. Ferric Chloride is used in the manufacture of printed circuit boards to etch the copper traces. It will also etch anything that has copper in it (bronze, brass). Admittedly this is a long etching time, but it wouldn't require the scrubber. Radio Shack sells small quantities (Ask for printed circuit board etchant or you'll get the deer in headlights look) you could try as an experiment, and then ramp up to commercial quantities if it worked for you.Bill Wyant
- Fort Worth, Texas
Cleaning flux residue from Aluminum without nitric acidOctober 14, 2016
Q. We are brazing Al tubing and there is a powdery residue and roughness around the brackets that are brazed to the tubes. Dipping in 50% nitric and H2O, cleans it up. Upper management is looking for something to substitute for the Nitric.Carl Cusanelli
Coatings Mgr. - Cartago, Costa Rica
^- Privately contact this inquirer -^
February 5, 2017
A. Hi Carl,
I'm not sure how practical it would be for your application but perhaps grinding, sanding, scotch brite or other mechanical step would clean up the flux residue.
Feather Hollow Eng.
February 9, 2017
A. You could save yourself a great deal of trouble by simply contacting the flux manufacturer.
Without knowing the chemical composition of the flux any suggestions are just guessing.