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Secondary (sealer) treatments on electrical fasteners

A customer has ask how a sealer may affect the performance of the screw fastener in his application. Hyprocoat 330 is applied of a zinc clear trivalent coating. The customer has noticed with some parts that the trivalent coating or the sealer causes problems when used in conjunction with locktite. The customer is concerned with the effects of heat cycling ( will it melt away leaving the zinc exposed), resistance to rust after assembly (is the sealer worn off exposing the ZInc) and electrical conductivity (does the sealer act as a resistor). Does anyone have any experience and can you provide any data to support your findings?

Alan Merritt
- HARRISON, Ohio
2006

I would suggest that the plater get together with the tech people at his supplier and get them to provide answers or to determine the facts based on sample pieces. This is called supplier customer service.

Gene Packman
process supplier - Great Neck, New York
2006

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I rarely feel any need to add to your responses, Gene, and there certainly is nothing wrong with your suggestion.

However, we in the finishing industry should admit that in the rush to come up with trivalent coating processes that would meet corrosion resistance requirements, other traditional requirements took a back seat -- including conductivity issues, adhesion of paint and powder coating, consistent coloration, compatibility with adhesives, etc. And the fact is that some of the proprietary approaches to trivalent coatings are superior to other proprietary approaches for some of these individual secondary issues. To tell the user to work with his supplier is okay, but we should also let him know that the approach his supplier took simply may not be as suited to compatibility with adhesives as the approach that other suppliers may have taken.

There were a number of technical sessions on these issues at Sur/Fin 2006; one, for example, discussed the many different ways to measure surface conductivity, and how the measured conductivity will vary radically based on the measurement method. The proceedings are already available from nasf.org and, although they do not include the very interesting panel discussions that took place, they probably will prove valuable to people battling these issues. 

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006