FTM 111: Zinc Flake Coatings

Fastener Training Minute 111: Zinc Flake Coatings

This edition of the Fastener Training Minute with Carmen Vertullo was originally published December 8, 2016 as “Zinc Flake Coatings” during episode 111 of Fully Threaded Radio.

Hi everybody, welcome to the Fastener Training Minute. This is Carmen Vertullo coming to you from the Fastener Training Institute and the Carver FACT Center in San Diego.

I had an interesting inquiry this morning regarding a coatings issue. One of my clients had received some product and a description of the coating did not quite match what it was supposed to be. They sent it to the customer that way, the customer saw the description of the coating, noticed the error and rejected the product. The problem was the description on the product was zinc and it only said zinc and the product was supposed to have what they perceived to be a zinc flake coating.

Doing some deeper drilling, I discovered that it’s probably a good idea that we should put a little more effort into how we describe coatings on fasteners and we return I’ll tell you what that description should look like and why it’s so important.

Today we’re talking about Coatings and specifically those that are generically referred to as “zinc flake coatings“, of which there are a variety of flavors. These coatings are very popular for the replacement of zinc electroplated coatings, especially in high-strength fasteners where we want to avoid the possibility of hydrogen embrittlement. In this case it was a 12.9 socket head cap screw. That’s a very high strength metric fastener, and the end user simply called out a coating that they generically referred to as zinc flake. It was generically bought as zinc flake and generically described as zinc flake.

The problem is that there are lots of implications when we change coatings not just for the prevention of hydrogen embrittlement, but for the application of the fastener in its intended purpose in terms of the tension. Each of these coatings whether they’re produced by a company such as Magni or Geomet or whatever they’re described as, or whether they’re described as an ASTM F1136 coating. Each coating has its own properties for friction which in turn affects its properties for tension. So it’s vital that the end-user understand the implications of calling out a zinc flake coating. It’s vital that the supplier know what is required and either some testing or at least some engineering effort be applied to knowing what the end result is going to be when they tighten the fastener down.

The good news is that it’s not hard to get this information. You can get it from a consultant such as myself, you can get training from the Fastener Training Institute, but the best source for this information is the IFI Fastener Technology Connections website.

Just keep in mind that when changing coatings, it’s not just a simple matter of calling out a generic coating, you need to use the brand name or the number or whatever term of endearment they used to describe their coding and or the ASTM or other type of specification.

This has been Carmen Vertullo with the Fastener Training Minute. I hope you learned something about coatings.

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