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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 trade names. "Chem film" is a 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

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

(note: this book is two volumes)

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2025: Martin may have been correct at the time, but MIL-DTL-5541 [⇦ this spec on DLA] is a current spec, it has not been replaced by an AMS spec.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