This edition of the Fastener Training Minute with Carmen Vertullo was originally published January 18th, 2022 as “are my fasteners RoHS compliant?” during episode 172 of Fully Threaded Radio.
Well, hi everybody, this is Carmen Vertullo with the Fastener Training Minute. Coming to you from the Fastener Training Institute in beautiful El Cajon, California where we are headquartered at our AIM Testing Laboratory.
Here at the AIM Testing Laboratory, we get many questions about fasteners and sometimes they revolve around fastener coating and plating, and sometimes they revolve around zinc coating and plating. And sometimes that revolves around: “How can I tell if these fasteners are RoHS compliant, And what does that mean?“. When I return I’ll give you some clues on how to tell if your zinc plating is RoHS or RoHS compliant.
Well, welcome back everybody to the Fastener Training Minute this is Carmen Vertullo and today we’re talking about zinc plated screws and RoHS compliance. RoHs means Reduction of Hazardous Substances and if you’ve been around this business very long you know that comes from the European Union. It’s one of the ways that they try to keep us filthy dirty Americans from shipping our poison over into Europe. One of the poisons that they try to eliminate is hexavalent chromium, which is very popular as a top coating on electroplated zinc articles including fasteners. It’s not so popular anymore, but it used to be very popular because it’s very effective and it is very low cost and in fact it’s not really that poisonous because there is not that much of it there and we’ve been using it forever with really no health effects.
If we process those Fasteners safely and properly it’s not that big of a deal. However they’re reaching into every little corner and trying to wipe out any possibility of anything so you cannot ship our hexavalent chromium coated fasteners to Europe anymore; we haven’t been able to do it for many years. But the problem is when you receive your fasteners whether they come directly from a manufacturer, or if they come from an importer, or if you are the Importer, or maybe you’re even sending them out to the plating shop and having them plated, you’re going to get some kind of top coat on that fastener and it is generally going to be either a hexavalent coating or a non hexavalent coating so how do we know?
Well first off, hopefully your fastener coating will come with a piece of paper, a certification of some sort, telling you what the specification to which it was plated was. And if we’re professional and we’re doing it right, it’s an inch fastener in the u.s. or even a metric fastener, that standard is going to be ASTM F1941/F1941M, the latest version. And in that standard when we designate what the top coating is, it’s going to be designated by a letter, and that letter is going to essentially tell us whether it’s got a color or no color. The letters are “A“, “B“, “C“, and “D“.
If we have an “A”, “B”, “C”, or a “D” at the end of our designation and that designation sounds like this: it sounds like FE/ZN which means steel fastener with a zinc coating on it. FE for this iron based steel and ZN for the zinc. And it’ll have a number like a 3 or a 5 or an 8 and that designates the thickness in micro meters, and generally that’s going to be 3 or 5 for Fasteners very thin coating the first one being around 1/10,000 of an inch if we convert it backwards a second one the 5 being around 2/10,000 inch and then comes the letter which is the color: clear, yellow, black. are the primary letters. But after that letter we can add another letter which would be an “N“, so instead of just an “A” it would be an “AN“. And so it sounds something like this as FE/ZN3AN. The trailing “N” designates a non-hexavalent topcoat. So if you have the trailing “N” in this designation and on the certification, your fastener is RoHS compliant.
Now in the world of metric Fasteners when we coat them, we have another standard which is very similar to this ASTM F1941/F1941M standard, and that’s called ISO 4042. There’s not a designation for hexavalent chrome, everything has a little “n” under it, its a little bit different designation system. But if we are plating to ISO 4042, and nowadays we can actually find plating shops in the U.S. that will do it, we can be assured that you have a designation under ISO 4042 that will include a non-hexavalent designation.
One other standard that you need to be aware of, and probably to be honest with you maybe one of our more common ones, is ASTM B633. We should avoid this standard for fasteners all the time, because it’s not a fastener coating it’s a coating for other types of articles, it even says so right in the standard. The standard says if you’re plating fasteners you should use ASTM F1941/F1941M. It says to avoid ASTM B633 for fasteners, but it’s still on lots of drawings and we run into it all the time. So if you have a certification to ASTM B633 and you need to know if your plating has hexavalent chromium or can it be RoHS compliant, those top coats are designated by types. Roman numeral I, roman numeral II, roman numeral III, roman numeral IV, V, and VI. So those types are how we determine what kind of top coat it has. And some have hexavalent chrome and some do not.
Type II is designated as a colored chromate coating, and it can have hexavalent chrome in it. It’s got the best salt spray results. By the way in ASTM F1941/F1941M as soon as you add that “N” for non-hexavalent chrome, in many of the categories your salt spray requirement goes down significantly. So be aware of that, it doesn’t necessarily mean the actual corrosion resistance is going to go down because those non-hexavalent topcoats are proprietary. You don’t really know what the hell they are, but they work pretty good these days. So just be aware that when you put that “N” in there, and want the non-hexavalent topcoat, you are sacrificing by specification, some corrosion performance in terms of salt spray testing.
Now back to ASTM B633. So Type II has a colored chromate coating and it can or probably will have hexavalent chrome. The other designations are called either conversion coatings or passivates, and those are designated to be non hexavalent-containing topcoats. So that’s how you can tell by looking at your certification. Now most plating shops will provide you with a RoHS certification if the product is RoHS compliant, and most of your fastener suppliers and your importers also be able to designate that your product is going to be RoHS compliant. But if you want to know, look at the plating certification and see what specification is listed and how the particular plating is designated.
Well that’s a little bit about coatings and platings, and a small little snippet regarding RoHS compliance of zinc plated fasteners. This has been Carmen Vertullo with the Fastener Training Minute, thanks for listening.