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Alodine for Marine Environment

Q. I'm looking to protect my sailboat outboard engine from corrosion in a salt water environment. The paint is in bad shape now and screams for replacement. Somebody recommended an Alodine treatment of the aluminum body prior to epoxy painting. a) Is this the right way to go, and b) where can I buy this Alodine. I called all the local paint etc. stores without success.

Walter Hecker
engineering - Fremont, California

A. I've had some limited exposure to the Alodine you ask about. There are many names for it, including gold Iridite. I found a product at the local automotive paint store made by Dupont, although many others make a similar product. It's called an aluminum prep #226S, step 1 and step 2. The first step is an aluminum brightener(acid). The second is a chromate....look out for the cyanide! You will be instructed to wipe on and rinse off. If this is a large project, I caution you, you will be using some hazardous and controlled chemicals. Not wise to rinse off on the ground. As with any paint job, prep is the key to success. The old paint must be completely stripped before this process will work for you. If its small parts, you should be ok. If not, I'd look for some commercial help. Good luck.

Paul Norman
Paul Norman
- Odessa, Texas

A. Try your local Automotive Paint and Body supply stores - I know at least a couple of our local suppliers stock it. It is typically supplied in small quantities as 'Alodine 1200s', which is a liquid concentrate used for brush-Alodine application. CAREFUL, though... It contains hexavalent chromium, ferricyanides and fluorides. Keep it off of yourself and catch & dispose of waste properly.

Mark McGlynn
- Oklahoma City, Oklahoma

A. Hi, Walter. Alodine is a product of Henkel, so they would be the starting point. These days trivalent chromate pretreatments are available from Henkel and others that do not have the toxicity of hexavalent chromate. If boating stores can't supply you, call a "plating process distributor". Good luck.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
February 26, 2009

April 8, 2014

A. Hi,

Alodine is a corrosion resistant barrier applied to aluminum and used primarily in the aircraft industry. It is very effective.

It is available from several manufacturers in liquid or powder form, (powder is mixed with water), and easily applied manually, spray, brush, sponge, dip tank etc., followed by a fresh water rinse. It leaves a chemical barrier etched into the surface reducing electrolysis. i.e., corrosion.
It is harmful to the skin, environment and requires personal protection gear. Read the MSDS. It has a shelf life.

Several distributors sell it, Aircraft Spruce and Sky-geek are two online retailers in the U.S. for example. It is Hazmat.

In terms of exchanging one for another... on your personal boat maybe okay... in the aviation industry not acceptable. Read the aircraft requirements carefully. If in doubt seek assistance from the aircraft or component manufacturer as most have an online hot-line or email contact for G.A. as well as engineering support for Commercial related questions.
Additionally seek assistance from the government regulatory commission for your country. FAA, DCA, LBA, CAA, etc. Most already have a continued airworthiness program based on manufacturers' recommendations on file from other operators and your aircraft may be listed in which case you can access additional information to better assist your needs. The manufacturer and current manuals are the first place to go, gov't regulatory commission second.
For example if an American built aircraft is being maintained in Brazil, let's say ... the aircraft should still be maintained to U.S. standards as set forth by the mfgr. and in the FAA (regulatory commission) circular 43.13. C available online at the FAA website. As long as those procedures listed comply with mfgr. recommendations. Followed then by the Brazilian aviation authority for their continued airworthiness program as additional steps may be required.

This forum is not the appropriate place for commercial aviation support. Perfect for marine, personal or general purpose.

I used Alodine on the aluminum air conditioner coils for my outdoor air unit at home, parts of my aluminum patio furniture and of course my homebuilt aircraft.

Hope this helps..


Craig Colby
- Fremont, California USA

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