| Author |
Message |
Jerome J. Lazar, RA, CCS, CSI, NCARB
Senior Member
Username: lazarcitec
Post Number: 1740
Registered: 05-2003
| | Posted on Thursday, February 16, 2017 - 10:26 pm: |    |
Contractor is claiming that aluminum that is to be welded can not be anodized? Anyone have any comments on this? |
William C. Pegues, FCSI, CCS
Senior Member
Username: wpegues
Post Number: 951
Registered: 10-2002
| | Posted on Friday, February 17, 2017 - 12:09 am: | |
Jerome,
Sometimes, google can be a truly good source. Here is a short discussion from 2006 about welding aluminum BEFORE anodizing. Mixed success, with cautionary advice, the rod is one alloy, the aluminum is another, and when they combine it becomes a 3rd alloy, and anodizing color depends on the alloy...so, some report success - some not so much.
http://www.finishing.com/403/64.shtml
If the aluminum piece has been anodized and is then welded, there is no telling what color you will get. Some alloys when reanodized turn yet a different color in the area where the anodizing was removed but not covered with the weld.
Your best bet is to contact a respected ornamental metal fabricator, or contact one of the manufacturers of aluminum railings and simply ask them how to accommodate the desired detail. What the GC is telling you may simply be passing on the comment of a sub who does not want to do the detail, regardless of the solution.
Still, welding after after anodizing - that's a coin toss for what the finish will look like.
William C. Pegues, FCSI, CCS, SCIP Affiliate |
J. Peter Jordan
Senior Member
Username: jpjordan
Post Number: 940
Registered: 05-2004
| | Posted on Friday, February 17, 2017 - 09:45 am: | |
I have the following thoughts:
(1) Best results are always from shop finishing after shop fabrication. This holds true for about everything.
(2) I would say that field welding aluminum is extremely difficult at best no matter what the finish.
(3) The comments above about variations in the finish are spot on.
(4) Welding color anodized aluminum (welding after finishing) would be a real no-no unless the welding is completely concealed in the finish work. There is simply no way to touch up an anodized finish.
(4) Welding aluminum with a clear anodized might be more acceptable; I would recommend a sample. I would think finishing welded aluminum before anodizing might be OK, but I would want to see a sample.
If you have to weld aluminum, I would recommend a paint finish (either liquid or powder coating). This gets around the issues with differing alloys and anodizing, and it can be touched up in the field.
Samples and mockups are your best friends where appearance is important.
J. Peter Jordan, FCSI, AIA, CCS, LEED AP, SCIP
|
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 1055
Registered: 12-2006
| | Posted on Friday, February 17, 2017 - 10:27 am: | |
William, thanks for looking that up.
Peter, I agree with you.
We are trying to get further away from anodizing for a number of reasons including the ones in this discussion. Most PVDF coating manufacturers can match anodized finishes pretty well at this point, the color variation is significantly reduced (better consistency), and there are some good 'green' coating companies out there now like Longboard (http://longboardcladding.com/) who have low-to-zero VOC in-shop options. |
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