No registration or passwords; no pop-up ads -- just aloha, fun, & answers.
(as an eBay Partner & Amazon Affiliate earns from qualifying purchases).
Home /
Site 🔍
pub  Where the
world gathers for metal finishing
Q&As since 1989


Iridite Coating and EPA listing


Dear Experts,

I am in the process of buying a business that used to do Iridite coating in-house. They now outsource that step. No one there seems to know what chemicals are used in the Iridite process and whether it could provide an EPA listed hazardous material situation. Could someone please explain what chemicals are used and whether there is a risk associated with the process. Many thanks in advance!


H.L. Singer
Sheet metal stamping and fabrication - Orlando, Florida, USA


Iridite is a trade name of a product used for MIL-C-5541 chromate conversion coating of aluminum. Yes, the process probably involved dipping the work into vats containing 1/2 to 5 percent solutions of hexavalent chromium. But there is no way to say from this distance that the process was or was not mismanaged in a way likely to leave hexavalent chromium in the earth or groundwater.

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


Would you please clarify that if Iridite's chemical solution must be "Hexavalent chromate".
How about Chemical conversion coating? If its solution is just hexavalent? Or can be other chromate solution?


telecom - Montreal, Québec, Canada

Hello Guoqing. Traditionally, most chromate conversion coating processes involved hexavalent chrome, so I think it's almost a sure thing that a plating shop that has been around for a while, like the one Mr. Singer is talking about, used hexavalent chromium in the past. But please try to describe your own situation.

As an aside, a Thunderbird was a 2-seat sports car, or a 4-seat car luxury car, or a 6-seat moderate-priced family car depending on how Ford chose to use the trade name in any given decade. Similarly, Iridite is a Macdermid trade name for a whole series of processes, and it means whatever the trademark holder decides it means.

Today with RoHS and WEEE requirements, there are many chromate coating processes that involve only trivalent chromium; Macdermid can choose for the Iridite trade name to be used only for hexavalent processes or for it to also cover today's trivalent processes. I suspect that some Iridites are hexavalent and some are not depending upon the particular number. Macdermid is your best source for such answers. Good luck!

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

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"