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Hardcoat Anodizing - Surface Area Calculation of a tube

When calculating the surface area of a tube for hardcoat anodizing (720 rule) should we include the inside surface of the tube? Specifically we have a tube that has a 7/8" diameter and is 11" long, do we use 30" or 60" squared? How far into a tubes interior surface will hardcoat penetrate?

Jeff Nathan
Anodizing Shop Manager - Bristol, RI
February 17, 2009

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February 17, 2009

Hi, Jeff. Hardcoat anodizing is a highly insulative coating, so you will get much better coverage inside the tube than you would get from non-insulative coatings like electroplating. I believe that if the parts are racked vertically, and you have very good solution agitation (which you should have for hardcoat anodizing), that you will get complete coverage.

Regards,

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

One way to find out is to take a scrap tube, anodize it and then do salami cuts with an abrasive saw about every inch or two. Use ball mikes and measure the total thickness of each of the sections. Keep the parts in order and log in the results in order and you will have a very good estimate of the coating on the inside of the tube.

James Watts
- Navarre, Florida
February 18, 2009