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Anodizing of iron and steel

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Q. Hi,

This is a great set of threads! I appreciate being able to read it. I don't understand: can iron (ferrous products) be anodized? How thick? What characteristics can be achieved? Thank you very much.

Harrie R. Buswell
- Berea, Kentucky, USA

A. Hi Harrie. All metals except gold and the rarer precious metals oxidize, forming oxide corrosion products on their surface. In some cases these oxidation products can be tightly adherent and non-porous, and thereby at least partially seal the metal from the environment and slow down the corrosion or otherwise comprise worthwhile coatings.

For some metals like aluminum it is possible to artificially produce this oxidation by making the component the anode under carefully controlled electrochemistry conditions, yielding a thick, attractive, and durable oxidized finish. That's called anodizing.

Iron and steel, however, produce a powdery, non-adherent, hydroscopic, porous corrosion product (rust) when they oxidize; and this is not effective in preventing additional corrosion. Therefore, to my knowledge it is not possible to beneficially anodize iron and steel. However if you explain what you are trying to do, we may be able to help you figure out how to achieve it. Good luck.

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

A. Anodized iron has a very niche application.

In terms of coloring and hardness associated with aluminum and titanium anodized films, the answer is simply "no".

Robert H Kinner
- Cleveland, Ohio
September 3, 2010

Q. I am wanting to create some form of electrically non conductive film or oxide on an alloy of 50% Iron/ 50% Nickel. The coating must be very thin .0002" or less and not have any outgassing properties. Any help would be awesome!

Mark Mandrell
- Agawam, Oklahoma, USA
September 19, 2013

A. Hi Mark. Even a well controlled thin e-coat would be 3X that thick. How 'non-conductive' must the coating be -- are you expecting it to actually serve as an insulator?


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

Can iron surface be covered with aluminium oxide film by anodising

Q. Can an iron surface be covered with aluminium oxide film by anodising?

Varma Mahi
- India
October 18, 2013

A. Hi Varma. Anodizing does not deposit aluminum on a surface, it converts aluminum on the surface to aluminum oxide. So, no, you can't deposit aluminum that way. You can, however, electroplate aluminum onto the surface (with a special non-aqueous process, not by conventional electroplating) and then anodize it. That does not mean, of course, that the average plating shop or anodizing shop could accomplish such a thing.

I would expect that it is possible to flame spray aluminum onto an iron surface or to hot-dip aluminize it, and then anodize it ... but I would anticipate a rather serious research & development effort would be necessary or the results would be imperfect and of questionable reliability.

Please flesh out this abstract question with your actual situation.


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

A. Picking up Ted's comments about non-aqueous plating of aluminium, a lot of work has been done on this by Karl Ryder at Leicester University (UK). He has published work on using ionic liquids to electrodeposit aluminium and he has some pretty good results. Once you have deposited the aluminium, it is relatively easy to anodize it to aluminium oxide by using conventional anodising systems.

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

A. One can deposit Aluminum on iron /steel by PVD and then anodize it. Thickness of Al coating, geometry of the component. etc., will have to be worked out.

H.R. Prabhakara - Consultant
Bangalore Plasmatek - Bangalore Karnataka India

Ed. note: We have other closely related threads which readers may find interesting:
Thread 37471 includes links to research on the subject of anodizing of iron and steel.
Thread 39602 inquires about possibility of chromate conversion coatings on iron and steel.

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