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Alodine Precoating as Metal Finishing

 

Does anyone know if there has ever been a legal or regulatory interpretation in any state as to whether the operation of performing Alodine conversion coating of aluminum, followed by painting, constitutes "Metal Finishing" under the definition of the Metal Finishing wastewater pretreatment standard (40 CFR 433.16)? The pretreatment standard mentions "Chromating" (undefined) as one of the covered Metal Finishing operations, but not chromate conversion coating prior to painting. Painting is not mentioned as one of the operations falling under this pretreatment standard, and, as the Alodine is an integral part of the painting operation to ensure adhesion, I believe it should be considered something separate from chromating. Personal opinions won't help me much, but will be considered.

Dennis Kirsch
- San Antonio Texas

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Well, it's an industrial waste and I believe that ALL industrial wastewater is covered by 40 CFR 403. So part of the answer is that if someone thinks it's not 433, but it is 403, they have to come up with a different subpart that it fits into better--so what subpart do they suggest? A second part of the answer is that it is generally the POTW's who have to administer the industrial pretreatment program and issue a permit--and I know that at least a few of them consider chromate conversion coating of aluminum to fit into 433. You can hunt around the Aluminum fabrication categories, but I don't think you'll do much different or better. Good luck.

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

"Chromating" is an accepted shortening of "chromate conversion coating". If you are trying to find a distinction between chromating and "chroming", then you might have something, but chroming refers to an electroplating (or finishing) process. IMOHO, you have a metal finishing operation that must comply with wastewater regulations.

Dan Brewer
chemical process supplier - Gurnee, Illinois
 

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Absolutely is!

You are finishing the metal surface with a regulated compound (chromium) and therefore are subject to the regulatory statutes.

By the way, are you also doing precleaning, acid pickling, and some type of zinc coating before you chromate?

If not - then you might consider looking at a chromate rinse recycle system, which would stop you from having any continuous discharge. Make DI water for better paint adherence, and you win on all counts. You will still have a di regen to either treat or dispose of, but most plants that we have installed them in have so little carry-over that a reasonably sized DI recycle plant may generate a few hundred gallons of waste per month - small enough to evaporate and drum and send off. Unless you go zero discharge, you will have to live with it!

Tom Baker
wastewater treatment specialist - Warminster, Pennsylvania

Thanks for the personal opinions - but I need an actual citation in which either EPA or a state environmental regulatory agency has made a formal determination as to whether chromate conversion coating of aluminum preparatory to immediate painting is/is not covered under the metal finishing categorical pretreatment section.

Dennis Kirsch
- San Antonio, Texas
 

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Hi Mr. Kirsch,

I was the environmental manager of a coil coating line for steel and galvalume, where we:

scotch brite brushed
alkaline cleaned
chromate conversion coated
painted

We accepted the fact that we were in the business of finishing metal using a simple interpretation of the CFR. All the coil coater's in the United States, as far as I know, have accepted this definition. Have you contacted the Coil Coater's Association for any guidelines they might have for their industry?

  
Tom Pullizzi
Falls Township, Pennsylvania

Going all the way back to the release of the categorical limits for 40 CFR413 in the Federal Register on Jan. 28, 1981, "These operations include electroplating, ... conversion coating, ..."

'Subpart E - Coatings Subcategory' says "413.50 Applicability: Description of the coating subcategory. The provisions of this subpart apply to discharges resulting from chromating, phosphating or immersion plating on ferrous and nonferrous materials."

An exception which was specifically excluded was "[2] Metal surface preparation and conversion coating conducted as part of coil coating (40CFR465)."

'Chromating' and 'chromate conversion coating' are used interchangeably in the regulation, in thousands upon thousands of literature references, as well as by thousands of people versed in the art because, as Dan Brewer says, they mean precisely the same thing. 'Chromating' is shorthand or slang for 'chromate conversion coating' and, sorry, it's simply not a matter of personal opinion. To argue on any basis that they are not the same thing, or that it was the intention of EPA to not regulate "chromating" or "chromate conversion coating" is, unfortunately, very obviously wrong.

If this is a legal issue you should see an environmental lawyer, the sooner the better. Best of luck with your situation.

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