ultrasonic issues

**apaul** · 04-25-2019, 06:31 AM

Hi All,

Not posted for a looong time!

Hope you can help

When I ultrasonic clean metal frames the coating flakes off

The machine is from a jewelery supplier could it be too powerful?

Many Thanks!

Alan

**lensmanmd** · 04-25-2019, 10:59 AM

What solution are you using?

**apaul** · 04-25-2019, 11:11 AM

Hi Lensmanmd,

Washing up liquid and warm water (you might call I dishwashing liquid)

Thanks!

Alan
I must bend light also! love that!

**Lelarep** · 04-25-2019, 02:10 PM

Originally Posted by apaul

Hi Lensmanmd,

Washing up liquid and warm water (you might call I dishwashing liquid)

Thanks!

Alan
I must bend light also! love that!

I'm betting these are frames that have taken some real-world abuse? If so, the machine is doing exactly what it is made to do, just too well in your case. Ultrasonics work by causing bubble cavitation. A cavitation is basically when a bubble is forced to collapse in upon itself, and it ceases to exist. When this happens it produces an extremely tiny focal area of intense heat and pressure because you are creating a temporary vacuum space. This is how ultrasonics clean things, they get between the surface and let's say a piece of dirt, collapse, and knock the dirt loose. The problem is, if you have a coating on a piece of metal that is not uniform and intact, said bubbles will get under that surface and do the same thing, which, as you can imagine, blows that coating right off the metal. Since the bubbles in ultrasonic cleaning are so small, they can enter imperfections we can't even perceive with the naked eye. I'm betting your machine is high frequency, 40 KHz range? As the higher the frequency, the smaller the bubble, and the smaller the features it can clean, and jewelry tends to have very small features one would want to clean. I would suggest trying a lower frequency machine, something in the 20 KHz range, much bigger bubbles, just as good as cleaning the large features on eyeglasses, and probably won't destroy anything. However, this will not fix the problem if the coating is poorly adhered or severely damaged, at that point nothing will likely save the coating from an ultrasonic attack.