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The seal coat on anodized parts is inhibiting an epoxy cure

2004

Our problem is:

We adhere a tiny aluminum bobbin to other tiny aluminum parts in the manufacture of industrial instruments. The parts are color anodized (sulfuric). Due to a recent juggle in the sourcing of these parts, we are having them anodized at a local plater instead of the vendor's shop. The problem is that at some point, the epoxy will not cure these parts any more. It is a special non-hygroscopic, one part, thermally cured adhesive. I believe that the new plater is using a different sealing method, and a component of the seal coat (probably the surfactant in a nickel acetate solution) is a cure inhibitor to the epoxy. We have had this issue once before with an older "lime" finish on aluminum and this epoxy. We have had this epoxy work with color anodized parts for over a year now and believe the epoxy is not the problem (not 100% sure about this batch of epoxy). The epoxy mfg. claims to have this batch of epoxy work with our parts by cleaning them with acetone [on eBay or Amazon]. I haven't been able to repeat that with many attempts. I have tried numerous solutions to treat the parts, alcohols, solvents, acids, etc. no success. This epoxy will cure Iridited parts. or bare parts. I may have the parts stripped and re-anodized with a boiled DI seal or no seal. Any ideas?

Ed
Mfg Engineer

Edward Doherty
instruments - Coral Springs, FL, USA

I believe we have a solution on this problem. Although we have a new anodizer for many of these parts, we still have many styles in stock from the original finisher. The epoxy would not cure those parts either. It is true that any high ph contaminant or moisture will be a cure inhibitor for this epoxy, but our current dilema cannot be caused by a finishing issue. What had happened was this batch of epoxy had been refrigerated to extend shelf life - that was a mistake. Every time it got opened, moisture would condense on the surface of the epoxy and dissolve into the mixture. This had a cummulative effect and created the cure inhibitor issue only on anodized finishes. A new batch of epoxy has been ordered, so problem is not 100% verified solved, but we are confident in it.

Edward Doherty
instruments - Coral Springs, Florida, USA
2004

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In either event, you wil get much better adhesion if you will bond the epoxy to UNsealed anodizing, then go back and seal after the epoxy has cured.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2004

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2006

Can you tell me what type of epoxy you are using for this application.
I have a similar need for an epoxy coating on anodized aluminum.

Thanks

Steven Roehlk
- Indianapolis, IN, USA