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How to do Aluminum anodizing

Q. How to do aluminum anodizing? What is the machinery required? What are the shades? What are the chemicals used in it. Please mail me as soon as possible.

Rohit Verat
industry - Mumbai, Mahashtra, India

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 :-)

"The Surface
Treatment &
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Aluminium and
Its Alloys"

by Wernick, Pinner
& Sheasby

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A. Hi Rohit.

There are many types of anodizing for many purposes, and many methods, but electrical power is applied to the part, usually while immersed in sulfuric acid, to impart a hard aluminum oxide finish. Nearly any shade of dye is available except white. But not much real progress can be made until you describe the parts; for example, the chromic acid anodizing of aircraft parts is very different from the hardcoat anodizing of wear surfaces, which is very different from the bronze colored anodizing of architectural extrusions. Good luck.

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


A. For plant design, equipment, materials of construction, solution heating & cooling, etc., see Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon (adv.)] . A plant with manual operations will differ from one with automated parts transfer in both initial & operating expense.

Use the 'Capital Equip.' link below to find vendors of rectifiers (power supplies), tanks, etc. Note that a hard anodizing rectifier must be capable of higher output voltage, 100 VDC, vs. 25 VDC for conventional anodizing.

US Specialty Color has a dye Color Chart and under Product Information, anodizing pretreatment chemicals, dyes and sealants.

Robert Probert's book, "ALUMINUM HOW-TO -- The Chromating - Anodizing - Hardcoating Handbook" details the anodizing procedures.
S. Kawai's book, Anodizing and Coloring of Aluminum Alloys [on on Amazon (adv.)], ISBN 090447724X, describes electrolytic ("two step") dyeing quite well. This is rather a specialty process for architectural aluminum and cookware in the USA, but seems more generally used in Japan.

Probably, you must establish a record for high quality anodizing over many years before chromic acid anodizing of aircraft parts is a consideration.

Before investing any money, be sure environmental permits can be obtained.

Ken Vlach [deceased]
- Goleta, California

contributor of the year 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, continue to benefit from.

Q. My client wants to have an antique bronze anodizing finish on aluminium window profiles. How do I achieve this -- what is the process?

Sunil Suryavanshi
Mumbai, India
May 18, 2012

A. Hi Sunil.

This would be sulfuric acid anodizing, with the coloration applied by what is called a two-step process rather than an organic dye. Metal salts are electrically deposited into the anodized pores before sealing, making the color very lightfast.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
May 21, 2012

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