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topic 25645

Will Forming Hurt Anodized Aluminum Pipe


A discussion started in 2003 but continuing through 2018

(2003)

Q. My company is installing anodized aluminum railings at a Waste Water Treatment Facility in Rhode Island. The system is a mechanically fastened system (as opposed to a welded railing system). The manufacturer we purchased the system from starts their fabrication with the pipe (1 1/2" sch 80 6063-T4)anodized. My question is whether or not bending (or forming) railing components AFTER the pipe has been anodized will adversely effect the integrity of the anodizing. On a sunny day, the bends appear brighter than the straight sections of rail, and looking closely, the bends seem cracked or scaled. Is bending after anodizing a common practice in the industry?

Follow-up question...Is there anything wrong with having one of these bends sent out and anodized again? Would it become darker than the rest of the railings that were only anodized once? Thank you for taking the time to read this inquiry, I hope it is of interest to the forum..

Sincerely,

Alan F. Mount
- Weymouth, Massachusetts, USA


(2003)

A. I have no personal knowledge of aluminum tube bending for railings, but technology keeps changing and improving, and just because some of us are not familiar with something doesn't necessarily mean it's no good. It could be it's a proven technology that I don't happen to know about yet. Maybe the cracks are so fine and well dispersed that blooming corrosion doesn't occur. But from book knowledge it sounds like a very big problem because the coatings are brittle and glass-like and surely crack during bending.

Color matching is difficult. If you send the parts out for re-anodizing they will probably come back darker, lighter, or just generally "off" in one direction or another. If you were able to send them back to the original anodizer they would probably be a lot closer.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


(2003)

A. Anodize is a ceramic. I do not know any ceramic that will not crack or break when slightly bent. I would bet a large Starbucks that you will see corrosion in at least a few bent portions within a year. Paint is an option.

James Watts
- Navarre, Florida


(2003)

Dear Ted.. in regards to my inquiry from last week, I have a few photos I would like to add if it is not too late...

Sincerely,

Alan F. Mount
- Weymouth, Massachusetts, USA


(2003)

A. It's not our role to get involved in a contract dispute from this distance, but now that you have sent photos I don't think anyone will takes James' bet :-)

From this distance the integrity of the anodized coating appears to be completely destroyed, and it appears that the answer is to strip and re-anodize them now that they are formed.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


(2007)

A. I build Ttops and fishing towers out of anodized aluminum pipe every day. We use pipe that is already anodized when we receive it. The finish on the bent sections seems to hold up fine on our projects, and nearly all of them are exposed frequently to salt water. Hope this helps

John Watson
- Chincoteague, Virginia


(2007)

i. That is quite interesting, John. Do you have any theory why you are able to bend your pipes without problems while the anodizing on Alan's pipe appears to be cracked to worthlessness?

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


(2007)

A. The coating does crack exactly like the pipe in the picture when we bend our pipe, its never really been an issue as far as corrosion goes. The coating does corrode in the environment that most of our work is subjected to, but it's pretty much spread out evenly and isn't concentrated on the bends in any way.

John Watson
- Chincoteague virginia


December 7, 2008

A. I have been Welding and fabricating anodized aluminum for quite some time. With the proper tooling and bending equipment you can greatly reduce the galling of anodizing in the bent area. Anodizing is a tough coating in general. From the look of the pics above, the bent section looks rough. I think using the right techniques it could be prevented.

Larry Trainor
- Bayville, New Jersey



April 3, 2012

Q. We have a building project featuring anodized aluminum custom exterior wall panels. As designed, these are to be formed of pre-anodized (clear) aluminum sheet. Now we are told that the finish can not be warranted along the fold lines, as "micro-crazing" might occur at this location.

Is this a well-known phenomenon? How deleterious is this to the anodized finish, and how visible is it likely to be in the completed wall? Will the crazing spread over time, with exposure to the elements?

David Nelson
- Piscataway, New Jersey, USA


April 4, 2012

A. The term "micro crazing" might not be the right word, but, indeed the pores will be spread and the seal broken open as a function of the alloy, anodic film thickness, and the angle of the bend. Corrosion places will open up. the unaided eye will not see the fracture until after the corrosion sets in.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como



Rotary Swaging, Rolling or Forming Anodized Al-alloy tube-end

January 18, 2018

Q. I am a final year mechanical engineering student and working on a minor project.

So, the idea is to create a bend along the entire circumference at the end of the tube inwards using rolling or, a more suitable process which anyone would suggest. The bend is to be achieved by a forming process. After going through several forums I have understood that any forming process would damage the anodized coating. So, I would like to get any suggestions on which process to use to achieve that section at the end of the tube and keep the anodized coating undamaged.

 __
/__\<---end section      |__|<-- Edge to be bent inwards
|  |                     |  |
|  |                     |  |
|  |<----Tube    Before: |  |              
Sivanand Devarakonda
- Hyderabad, India



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