Ken Kobayashi <
[email protected]> wrote in
news:74[email protected]:
> On Wed, 22 Jan 2003 05:42:27 GMT, "Tho X. Bui" <
[email protected]> wrote:
>>Do remember that a true ultrasonic cleaner and aqueous solutions can be very bad for aluminum
>>parts because of hydrogen embrittlement. Toss in a piece of foil, let it run for 15 minutes and
>>you'll find it disintegrated.
>
> Do you have a cite for this? I tried to look into this and found no concrete information. At work
> we use ultrasonic cleaners to clean aluminum components and nobody seems to know about this
> danger, if it exists at all.
>
> Ken Kobayashi
[email protected]
>
Although I am certainly no expert, nor even well versed on the subject, I can find only two
references to hydrogen embrittlement of aluminum. Always mentioned are high tensile steels, and
especially those that contain nickel. Apparently, this is a subject wherein a consensus has not been
reached.In all but one article,ultrasonics are not mentioned, only corrosion, and most often
circumstances of plating baths. I quote the article that mentions aluminum and titanium:
> Hydrogen Embrittlement: A General Observation
> Dr. Paul Ray, FIMF, London, England When atomic hydrogen enters steel and some other metals (such
> as aluminum
and titanium alloys), it can cause loss of ductility or load-carrying ability, cracking (usually as
submicroscopic cracks) or sudden catastrophic failures well below the yield strength or even the
normal design strength for the alloys. This phenomenon often occurs in alloys that show no
significant loss in ductility when measured by conventional tensile tests, and is frequently
referred to as hydrogen-induced delayed brittle failure, hydrogen stress cracking or hydrogen
embrittlement (HE). HE can also be observed in very clean iron and steel. Even mild steel and dead
mid steel are considered to be susceptible under certain conditions. Because of the complexity of
the problem, however, the results of research differ considerably from batch to batch of the same
material, from material to material, from laboratory to laboratory, from one test to another, and so
on. Considerable research has been carried out in the past 40–50 years with inconclusive and often
confusing results. The potential hazards of HE from the electro- and autocatalytic plating processes
of high-strength carbon steels have long been recognized in the plating industry, and in pre- and
post-plating heat treatment. Some test methods are specified in International Standards. These
standards, based on research and field work, merit recognition from the plating industry and will be
discussed in this paper.
>>
The second article specifically mentions the "aluminum foil test" and was found at
http://aec.army.mil/usaec/technology/p2compliance10.html
> Coupling (or the transfer of energy) between the transducers and the
liquid medium is critical. A quick test that can be conducted to determine if the intensity of the
cavitation is adequate to provide aggressive cleaning action is the aluminum foil erosion test. To
conduct this test, simply submerge a 0.001-in. thick piece of aluminum foil in the tank while it is
operating for 30 sec. A good aggressive ultrasonic tank will cause holes to form in the foil. This
test also is useful in determining where any dead zones may occur in the tank. To ensure that parts
are not left in dead zones during cleaning, it is advisable to rotate the parts in the tank.
>
As far as Bill's HomeMade ultraSonic Cleaner, I believe it is likely sonic, rather than ultrasonic.
One might be able to determine a rough estimate by consulting the label on the massager and
identifying the rotational speed of the motor. Sonic cleaners are quite effective, so I have no
doubts that Bill's cleaner does a fine job.
happy trails, rorschandt
