Where the
world gathers for metal finishing
Q&As since 1989


-----

Will Ultrasonics remove smut?

After stripping Nickel from Compressor Rotor Wheels, there is a layer of smut that develops on the part. We have to remove the smut before dipping the wheels back into the stripping solution again. We currently remove the smut by wet blasting but this takes up a lot of time. I'm wondering if ultrasonic cleaning will be able to remove this smut. If not, what other methods are there? The compressor wheels are about 14" in diameter, 2" thick.

This is the chemical used to strip the NiCd. "Metex Nickel Stripper SCB" from Macdermid This is a two part bath composed of part SCB-A, described by the manufacturer as a salt of nitro aryl sulfonic acid and of part SCB-B, a combination of ethylenediamine and ammonia [on eBay or Amazon]. SCB-A is most probably the sodium salt of nitrobenzenesulfonic acid. In SCB-B the ethylenediamine is a strong base.

Alvin Kok
- Oakland, California
2003

If by wet blast you mean vapor hone, yes it will take a fair amount of time. If you mean a high pressure water blast with a compressed air added, it should be the fastest way to get it completely off. Ultrasonics will work with the correct additives but it will probably be slow and a mess requiring frequent dumping. I trust that this nickel-laden waste is going to the waste treatment system where the edta is going to adversely affect your ability to meet disposal specs.

James Watts
- Navarre, Florida
2003

Thanks for the reply James. The smut is actually extremely difficult to take off. Even with wet vapor hone (with Aluminum Oxide media) it takes quite some time, I do not think that pressurized water and air will do the trick. The layer of smut is actually just a very thin layer. It seems like it's baked on. I've tried using a alkaline rust remover/cleaner, and ultrasonics at 40kHz with a soapy solution (Brulin 815GD) as the medium all with no avail. Anybody got any suggestions?

Alvin Kok
- Oakland, California
2003

Many shops that are plating and stripping nickel use a chromic acid dip to remove the nickel smut that forms during the stripping process.

Dan Brewer
chemical process supplier - Gurnee, Illinois
2003

---

Alvin,
You mention NiCd plating. Is this the Nickel first and then Cad plating per aerospace spec? If so the baking process of this spec may be causing some diffusion into the base metal. Give some feedback and I'll try to remember how we used to strip it at the airline, can't recall at the moment...I think we used a cyanide based nickel strip (Stripping the Cad first in Ammonium Nitrate) but don't quote me on that as it may cause hydrogen embrittlement problems.

Jon Quirt
- Minneapolis, Minnesota
2003

A vapor hone works on a suction method and is very slow. We had a British built cabinet that pumped the water/slurry with air injection. This worked at about 100 times the speed of the vapor hone. It is very much like comparing a siphon dry blast cabinet to a pressure blast cabinet. The strip that I had used was a permanganate based and you had to get out of the hot solution into the rinse tank fast or the black mud would dry and then was extremely difficult to get off. Once it was cold and wet, we used scotchbrite - wet- and then an acid dip and back into the strip tank. It was a pain.

James Watts
- Navarre, Florida
2003

---

You might try warm cyanide dip to remove that smut.

Neil Bell
Red Sky Plating

Albuquerque, New Mexico

2003

The smut can easily be removed with Bio detergents.

Edward Petermann
- Kitchener, Ontario, Canada
2003

---

The customer's spec states 5 minutes of air-water blast to remove smut after Degreasing/Cleaning, Nitric Etch, Nitric HFS Etch and Ammonium Bifluoride Etch. This is on Titanium Blade Disks.

What is the pressure of the water and air?
Is there a high pressure pump?
Do we use an intermittent air supply while passing water through a water nozzle?
Will this contribute to smut removal beyond the first point of impact down within the spaces obscured by the curving blade?

Joe Lyons
- Farmington Michigan
October 6, 2009