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Clear anodized aluminum repair: what finish / coating to use?




Q. We have fabricated aluminum handrail which has been anodized. After the handrail returned from (clear) anodizing it was noticed that the 1" long skip welds attaching the toe plates to the handrail were not fused on the plate side and will require repair. What is the best process available to coat the localized repair areas short of re-anodizing.

Note to those reading this. This is not the first time we have noticed that weld defects on aluminum fabrications have become visible after anodizing that were not noted during visual inspection prior to anodizing. Dye penetrant inspection of welds prior to anodizing may be beneficial in detecting these type of hard to see defects on critical weldments prior to anodizing.

Vince Archibald
- Clackamas, Oregon, USA
2001


A. Hi Vince. A chromate conversion coating (Iridite, Alodine, Chem Film) per MIL-DTL-5541 [on DLA] of the weld areas should be satisfactory. Pen-type touchup kits are available. Expect functional rather than decorative results. Good luck.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001




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Q. I am a project manager for a metal fabrication shop. Recently, we made some aluminum handrail that is clear anodized. Some of the handrail was damaged during install. The damage requires some welds to be redone, major gouges to be repaired, etc. needless to say there will be areas that the Anodized finish will be removed. Is there a spray or brush on coating that I can apply once the repair is done that will blend in with the anodized finish?

Jason Swartz
fabrication - Columbus, Ohio
2006



A. Are you contractually obligated to furnish anodized aluminum?
Choose a filler alloy that will give a good color match after anodizing: 5356 filler for welding 5052, 5086 & 6063, or 5654 filler for welding 6061. More info is available from welding suppliers (Harris, Lincoln Electric, Miller). Not possible to match the grain size, however.
Remove existing anodize from edges to be welded, to avoid oxide inclusions in the weld.
After welding, some mechanical finishing (smoothing, graining) will be necessary.
Brush anodize. Liquid Development Corporation has info, chemicals and equipment. Your anodizer may be able to perform the field work.
Finish with a clear, polyurethane marine varnish.

Ken Vlach [deceased]
- Goleta, California

contributor of the year Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

2006




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Q. I require a way to match clear anodizing.

I build aluminium full scale mock ups of window frames for high-rise buildings and frequently modifications mean raw mill finish edges are seen; is there a way to match the clear anodize effect (only visually) the mockups are temporary so only a visual temp match is needed?

Any help is appreciated.

Thanks

Darshan Naik
- Brisbane, Australia
June 10, 2009




Change black anodize to clear

Q. We quoted a job to supply black anodized aluminum rail. They now want clear anodized aluminum rail. Is there a cost difference?

Rick Valente
- Smithfield, Virginia
September 19, 2013



probertEthumb Aluminum How-To
"Chromating - Anodizing - Hardcoating"
by Robert Probert

You'll love this book. Finishing.com has sold 880 copies over the years without ever a single return request :-)


A. Hi Rick. Clear anodizing might be slightly less expensive because there is no need for a dye step. But, perhaps more importantly, clear anodizing can be less expensive than black because it can usually be half as thick and therefore take only half as much anodizing time and current.

The explanation is that anodizing can usually perform very well at a coating thickness of .0003 to .0004" thickness (or less), whereas to get a rich saturated stable black color may require an anodizing thickness of .0006 to .0008" (basically, you can't get enough dye into the pores for a good saturated dark color if the anodizing thickness isn't sufficient).

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 23, 2013




Q. I'm at the back end of installing close to 30,000 sq ft of Curtain wall, in clear anodized finish. I've been trying to match a paint that will blend in with the frames as some of them have been scratched by other trades, during install, etc. Some of the scratches are through the finish. Is there a way, other than paint, to repair these areas?
Thanks in Advance!

Laird Cross
Glazing - New Orleans, Louisiana United States
June 6, 2015


A. First: if the anodizing has been scratched, is quality bad?
Second: you can repair the anodized aluminum with 650 cromital. In the specification it tells you how to use it

Victor Solis
- Guadalajara, Jalisco, Mexico
June 25, 2015




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