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Iridite finish spec for aluminum

Quickstart:
Aluminum is often 'chromate conversion coated' as a corrosion resistant final finish or as a pretreatment for painting or powder coating. The process actually involves many steps, usually including alkaline cleaning, etching, deox/desmut, the chromate conversion step per se, and water rinses between each step.
MIL-C-5541 / MIL-DTL-5541 / MIL PRF-5541 is the most commonly cited spec. "Alodine" and "Iridite" are proprietary trade names of the suppliers of the process chemistry. In the USA "Chem film" is an often used slang term for the process.

Q. My company has inherited a design including aluminum parts which are specified to be finished according to "~~IRRIDITE~~ ^ ^Iridite 14-2". The shop that is now making the parts doesn't recognize this spec, and I have been unable to find it on the web or in any of the reference books I looked at.

Can someone enlighten me as to what this spec is?

Thomas McCarty
- Lake Forest, California, USA
2001

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. Iridite is a Macdermid trade name for chromate conversion coatings, Thomas. Note that it has a single 'r', which may be why you had difficulty with your search.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.

A. Tom,

14-2 is not a spec it is a product, originally from Allied Kelite. It is a gold chromate on Aluminum. The spec is MIL-C-5541. And 14-2 meets it. There are non-chrome substitutes for 14-2 such as Sanchem 3500.

Drew Nosti, CEF
Anodize USA

Ladson, South Carolina

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

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or AbeBooks

(affil link)

A. Iridite 14-2 is a trade name for a chem film process like Alodine 1200.

What you could do is to change the spec to AMSC5541 class 1A (replaced Mil-C-5541 class 1A). This will get you from a trade name to an internationally recognised standard.

Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

Ed. update Mar. 2025: Martin may have been correct at the time, but MIL-DTL-5541 [⇦ this spec on DLA] is a current spec, it has not been replaced by an AMS spec.

A. Iridite 14-2 is a product.

There are many products used for chromate conversion aka chem film aka chemical conversion coatings.

Iridite 14-2 is just one of many products used to produce these coatings.

This happens to be the product we use here.

David A. Kraft
- Long Island City, New York

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