finishing.com -- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

HomeFAQsBooksHelpWantedAdvertiseForum
topic 598

Dielectric strength of anodized coatings


(1996)

Hello fellow finishers,

My question is regarding anodic films produced from sulfuric acid baths ( Mil-A-8625 [link is to free spec at Defense Logistics Agency, dla.mil], Type II, class 2) on a 6061 T-6 alloy. Does anyone have information on dielectric strength of these coatings and how one would go about measuring this property? Thanks in advance for your help.

Keith Wicklund, CEF-SE
avionics - Minneapolis, Minnesota


(1996)

I recall seeing values for specific breakdown voltages for sulfuric acid films around 40 V/micrometer of oxide thickness. There is a commercial instrument to measure this, although I do not remember the vendor. It essentially consists of an electrode of known area, that is put onto the surface with a spring, so there is a constant force, and a high voltage AC power supply. The voltage is increased until a sudden voltage drop occurs which indicates breakdown of the film. See ASTM B110-45 (1973).

Gary A. Nitowski
Alcoa Center, Pennsylvania


(1996)

Thanks, Gary. That tells me what I need to know. Apparently, dielectric strength is not considered to be as important as other properties of anodic films because ASTM B110 has been discontinued with no replacement mentioned. The only other source of information I could find on the topic was an Electroplating Engineering Handbook>. The values they mention there seem to be consistent with those you mention. Thanks again for your time.

Keith Wicklund, CEF-SE
avionics - Minneapolis, Minnesota


(1996)

Get a copy of the mil spec for anodizing. it used to have methods and values. obviously it depends on the thickness and the density of the film. Even has the unit for testing. One square inch of copper under a given pressure and voltage. If you can not find it, write and I will look for it.

James Watts
- Navarre, Florida


(1996)

My previous comment blew it. It must have been in a cross reference document. If you will e mail me the ASTM number, I will see if it is in an old data base that I have access to. Sorry for the stupid booboo.

James Watts
- Navarre, Florida


May 22, 2012

A. I have used a DC voltage from a short circuit protected power supply to test as a measurement of anodize quality. Low quality anodize will arc at voltages less than 300. Most good anodize will go to 600V or higher. It is a method that I use and it is not based on any particular standard, just years of experience with various suppliers and geometries. I just use simple voltmeter probes and just rub them on oposite sides of the part. Be careful not to become part of the circuit!!!

Matthew Thie
- indianapolis,Indiana USA



This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.