ASTM F1941 / ASTM F1941M are important updates to ASTM B633 for plating fasteners.
This edition of the Fastener Training Minute with Carmen Vertullo was originally published April 18, 2019 as “An Important Fastener Standards Update” during episode 139 of Fully Threaded Radio.
Today’s topic is an important fastener standards update that you need to know about, and that standard is ASTM B633. ASTM B633 is actually not a fastener standard, it’s a plating standard for zinc electroplating, and it’s actually not even a fastener plating standard.
Well as most of you know who plate or specify plating for Fasteners, ASTM B633 has been the prolific standard that has been used for all kinds of zinc electroplating over the years, though its not ideal for fasteners. So in the year 2000 the ASTM committee F-16 on Fasteners developed a new plating specification specifically for fasteners. That standard was ASTM F1941 to help solve the problems associated with ASTM B633 when it’s used for fasteners. Since then ASTM F1941 has been continually improved and we now have F1941 / F1941M-2016, which is the definitive specification for electroplating fasteners, in that it includes metric fasteners as well. So I’ll just say out of the gate that ASTM F1941 / F1941M should always be used for electroplating fasteners.
Don’t use ASTM B633 now, because unfortunately in addition to not being well suited for plating fasteners, ASTM B633 has changed for the worse over the years. Primarily, ASTM B633 changed the requirement for hydrogen embrittlement relief baking to require pre and post baking of steel parts above HRC C31, (Rockwell Hardness C31). Research has shown for some time now that only steel parts above HRC 39 are susceptible to electroplating induced hydrogen embrittlement. And that’s the requirement for baking in F1931. Now the problem for us fastener suppliers is that many older drawings and specifications refer to ASTM B633 for electroplating fasteners, and that’s a problem because it’s not ideal a lot of time and money has been wasted in unnecessarily baking electroplated Parts when B633 is specified.
Well, the good news is this: after many years of work and countless meetings and ballots, the ASTM committee BO8 on Coatings, which I serve on, has approved a change to that spec to require baking only on Parts above HRC 39 in line with ASTM F1941 / F1941M. So the next time you look at ASTM B633, the newer version will reflect that change. This is an important change for suppliers, platers, and end-users alike. For the informed faster user, it will save a lot of money and energy and provide shorter lead-times. In any case we should still always use ASTM F1941 / F1941M as the specification for electroplating fasteners. Even when ASTM B633 is called out.
Now you might say how can I use a ASTM F1941 when ASTM B633 is the call out? Well the authoritative reference for doing that is in the introduction to ASTM F1941 / F1941M where it says “this standard shall be used in place of ASTM B633 for mechanical fasteners“. Now if you are a supplier and your customer calls out ASTM B633, be sure they are informed and concur, and let them know that their certification will read ASTM F1941 / F1941M. Now if you have any questions on properly translating an ASTM B633 plating designation to ASTM F1941 / F1941M designation, AIM Testing Laboratories is happy to help you with that. We are easy to get ahold of at info@aimtestlab.com. So the bottom line is this: ASTM B633, the problem is solved, but don’t use it for fasteners, use ASTM F1941 / F1941M instead.
And many thanks to our fastener professionals, especially Dr. Salim Brahimi who serves on both the ASTM F16 and BO8 committees for working towards the solution.