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Sticky surface after anodising

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Q. I recently got some computer side panels stripped of their black anodizing and re-anodised in clear.

Photo of original finish:


The finish I was hoping for:


for Shops, Specifiers & Engineers

"Aluminum How-To" -- Chromating, Anodizing, Hardcoating by Robert Probert (2005)
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"The Surface Treatment & Finishing of Aluminium and Its Alloys" by Wernick, Pinner & Sheasby (1959 - 2001)
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"The Metallurgy of Anodizing Aluminum" by Jude Mary Runge (2018)
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"Surface Treatment and Finishing of Aluminum" by Robert King (1988)
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"Anodic Oxidation of Aluminum and Its Alloys" by V. F. Henley (1982)
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"Aluminum Finishes Process Manual" by Reynolds Aluminum (1973)
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When I got them home and opened the package I noticed that they are far more yellow (photo attached) than I had hoped and are slightly tacky to touch.

There are also black spots on the panels in unfortunately obvious locations (assumedly from where the pieces were held while stripping), but the company I took them too has graciously offered to reprocess them for me free of charge.

I will obviously ask about the colour/texture when I take them back, but I was hoping someone here might be able to clarify whether it is realistic for me to expect a "nicer" finish, or if it is simply caused by the alloy etc.


D Pearson
- Melbourne, Australia
January 19, 2024

A. Hello D,
Probably neither you nor we know the alloy, but if it's offered in clear and black it's probably a suitable alloy for decorative anodizing. "Stickiness" or "tackiness" is almost always a sign of insufficient sealing.

We didn't receive the pic of what you actually got (you can attach it in email to, but it sounds like you've hooked up with a responsible anodizing shop who wants to make things right; I think you can expect it to look the way you hope, with no yellow tint nor black spots.
Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

⇩ Related postings, oldest first ⇩

Q. Sometimes after anodising we obtain a sticky fell to the surface of our aluminium parts. Has anyone come across this issue and is their a method of eliminating this.

Denis Hoyle
anodiser - Nelson, England

Ed. note: Our readers have most often attributed this to improper sealing. Please try searching the site for "sticky seal".

A. Usually the surface is sticky immediate after anodising i.e that indicates either no sealing or insufficient sealing. A die absorption test will confirm this. The remedy is to put back the anodised material to Seal tank for the time require in accordance with the total film thickness.


Srimay Basu
- Dubai, U.A.E.

A. I reckon this is due to poor sealing. Check you process parameters and specifications and just to prove the point, try dying the anodised layer and seeing if it stays fast.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

A. Inadequate rinsing after anodising often can contribute to the problem faced by you. Try at least 2 rinses and thereafter proper sealing as already suggested by other readers.

Malvinder Pal Singh
- Delhi, India

Q. Hi,

I'm adding new sealing tank with nickel acetate (warm sealing with temp 60 - 70 °C) to speed up my productivity. However I'm still using my old sealing/old tank (cold sealing, nickel fluoride especially for my EC coloring). Sometimes I found some pieces sticky for clear and color coating upon warm sealing or cold sealing. Is there someone tell me what is the reason? Is it because I'm using the same rinsing for both seals? Please advise.

Roni Panjaitan
- Surabaya, East Java, Indonesia
April 17, 2012

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

Also available in Spanish

You'll love this book. has sold 891 copies without a single return request :-)

A. Nickel acetate and acetic acid are "sticky", you are not rinsing it off.

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

A. Sticky = poor sealing.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

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