How to do White Anodizing

A. There's a simple answer to this. Its not possible to anodize white. I've asked myself, and the guy I buy my dyes from said "If you find a way, you'll be a millionaire". So I guess that pretty well sums it up. Its just not possible to anodize white.

"The Surface
Treatment &
Finishing of
Aluminium and
Its Alloys"
by Wernick, Pinner
& Sheasby

(note: this book is two volumes)

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

Also available in Spanish

You'll love this book. Finishing.com has sold almost a thousand copies without a single return request :-)

A. Well, now all the 'home anodizers' out there who feel that anodizing is safe and easy have a mission and a way to turn their hobby into a major business if they are successful.

A. YKK API America, Inc. in Dublin, GA makes white anodized finish!

Maybe, Matt. They say they offer white on their website, but they also claim they put electrostatic organic topcoats over their anodizing; so it's not really clear that this 'white anodized' finish would be white without the organic (paint) topcoat. If there is a white dye available, or a white two-step coloring process, I'd still like to hear about it. I've never researched the reasons for it's reported unavailability, so I can't say much except that I've never seen or heard of a white dye.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

A. I was just noodling around wondering if anyone else was developing a white anodize, besides the company I work for. We're developing a White Anodize right now. There are some real difficulties to the processing, but we have some of the rather difficult things taken care of. Maybe someday it will be a commercial process. But for now, all I can say is that it's in R and D.

A. Hi, Nassif. Look into electrophoretic lacquering; this is very thin, and white is no problem.

Hi, Catherine. "White anodizing" does not have any special meaning -- it simply means anodizing that has been dyed white rather than some other color. White is apparently difficult -- perhaps due to the fact that dyeing is a subtractive coloring process and white is the presence of all colors? That's a guess, not an explanation :-)

Letter 20562 claims some methods, and describes a dyeing procedure which will get you to at least an off-white. Good luck.

A. The anodizing in white is possible.

Please read the following pdf document to see how they did it.

www.italfinish.com/public/images/documenti/aacwhiteanod.pdf

Hi, Iaroslav. Thanks for the very interesting paper! I'm not sure if it's really legitimate to call a process "aluminum anodizing" when it operates in alkali rather than acid, operates at hundreds of volts instead of 12-18 volts, is not necessarily anodic because no details are revealed about the power supply, and the process occludes various non-aluminum & non-hydroxide chemicals into the coating -- but it clearly is a way of generating a white inorganic and interesting coating. I wonder is this is, or is similar to, the "Kepla-Coat" that Paul mentioned? Thanks again!

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 8, 2009

A. I am a mere hobbyist electro-plater but do have expertise in dyestuff so hope I can shed some light on the white anodising dilemma.
White dye simply does not exist. It is a question that as a dye supplier, I regularly get asked; can I dye this (whatever) white? For reflected colour (which is almost exclusively how we see light) white indicates a total absence of colour. If you think about the process of bleaching, that is using a reducing agent to remove colour with the end result of ......... white.
The closest thing thing in the dyestuff world to white is optical (fluorescent) brightening agents (FBAs). The Society of Dyers and Colourists' (SDC) Colour Index classifies dyes into eight colour groups; yellow, orange, red, violet, blue, green, brown and black. Notice NO WHITE.
The anodising dyes are a selected groups of dyes that by experimentation have been shown to colour the unsealed surface of anodised aluminium AND have high light fastness; typically in the order of 7 to 8 (on a scale from 0 to 8). In my experience, they all seem to be premetalised acid dyes, which are an organic/inorganic hybrid molecule.
Pigments however are a different story and do include white; the common ones being zinc oxide ⇦ this on eBay or Amazon [affil links] and titanium dioxide ⇦ this on eBay or Amazon [affil links] . The main difference between dyes and pigments is that dyes are soluble and pigments aren't.
So could white pigment be used to colour anodising? Probably not due to the difficulty of keeping the pigment in suspension (not insurmountable) but I believe the main reason being the size of the particles. Not sure what size the 'holes' in the unsealed anodising are but while dyes typically dissolve into solution as individual molecules, pigments disperse as MASSIVE clusters of molecules.