The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Surface treatment for EN AW 1050A Aluminum (European spec)

I have a customer that is asking to have a part which is manufactured from EN AW 1050A Aluminum coated with a surface treatment that has a insulation resitance greater than 100 Mohms under 500v for (2) seconds.

It must be economical and in bulk because the volume is 20,000,000/year. The part is fairly small with a weight of 0.005 lbs/each.

Any suggestions? We will start the project off here in the U.S. but it will eventually end up in the Czech Republic so the treatment hopefully will be available there as well.

Thanks in advance for any help you all can give.

Kevin Johnson
Designer - Waterbury, Connecticut
March 8, 2010

---

Hi, Kevin. I'd talk to a bulk anodizer and see what they say. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 8, 2010

I have tried calling many anodizing companies and NONE have a clue!

Anyone out there know of a finish for Aluminum that will meet this specification so I can direct the finishers on what they should quote.

Thanks

Kevin Johnson
- Waterbury, Connecticut
March 11, 2010

---

Kevin,

I agree with Ted that a bulk anodized finish is a good option to investigate. Accurate Anodizing and Anacote Corporation [Ed. note Jan 20100: Anacote is no longer in business] are two suppliers in the USA. AHC Oberflaechentechnik in Germany would be a possibility for European production. When you say that the anodizers you have contacted have no clue, do you mean that they are not guaranteeing that an anodized finish can meet your insulation resistance specification? Keep in mind that these are suppliers of coatings/finishes, and that they are not necessarily familiar with this type of specialized testing. You may want to perform some Google searches using keywords like dielectric strength, breakdown voltage, etc. in order to see what information may exist in research journals, etc. on the electrical properties aluminum anodic coatings.

Toby Padfield
Automotive component supplier - Michigan, USA

Hi Kevin,

I saw your posting when it first appeared and intended to reply. For some reason my failing brain decided that it was in the "Anodising" section and that it had been lost! Thanks to Ted Mooney for putting me right.

Ancient British Anodising Standard BS1615 included a test method for determining anodising film thickness by voltage breakdown. As I recall, a film of ~ 0.0005 inch (12um) would breakdown at ~ 500 volts. I can more-or-less remember the design if that is of any use - strange that I can remember details from the 1960's but not where I saw your letter a day after it appeared!
Usually bulk anodising is used to give films of less than 0.0005. You do also get areas of no anodising where contact is made from one component to the next.

It is not sufficient to call for a resistivity without stating the surface area over which it is to be measured. The test method for measuring the resistivity would be critical. My only involvement in such measurements was in checking sealing quality. Here a liquid contact is made to the anodised surface and admittance is measured. As a reminder, admittance is the equivalent to conductance but using AC rather than DC. And the inverses of these are impedance and resistance.

You need a proper test methods for both.

Are you still checking for replies? Is this of any help?

Harry

Harry Parkes
- Birmingham, UK