ASTM F1941 - zinc plating high-strength cap screws?
ASTM F1941 - zinc plating high-strength cap screws?
(OP)
Ok, it may have been done to death, but I had not heard of the ASTM F1941 and its cohort spec. F1940 before. A quick search failed to deliver a succinct answer.
If zinc plating is applied per F1941, can an ASTM A574 alloy socket head cap screw be reasonably said to be free of hydrogen embrittlement?
Or are does the standard warning (don't zinc plate on steel with tensile strength > 150 ksi) still apply?
My fallback is to specify a good zinc-rich primer paint or similar anti-corrosion coating on standard black oxide finished fasteners.
If zinc plating is applied per F1941, can an ASTM A574 alloy socket head cap screw be reasonably said to be free of hydrogen embrittlement?
Or are does the standard warning (don't zinc plate on steel with tensile strength > 150 ksi) still apply?
My fallback is to specify a good zinc-rich primer paint or similar anti-corrosion coating on standard black oxide finished fasteners.





RE: ASTM F1941 - zinc plating high-strength cap screws?
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RE: ASTM F1941 - zinc plating high-strength cap screws?
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Regards,
Mike
RE: ASTM F1941 - zinc plating high-strength cap screws?
"Although this risk [of hydrogen embrittlement from plating] can be managed by selecting raw materials suitable for the application of elecrodeposited coatings and by using modern methods of surface treatment and post heat-treatment (baking), the risk of hydrogen embrittlement cannot be completely eliminated. Therefore, the application of a metallic coating by electrodepostiion is not recommended for such fasteners [HRC > 40]."
Weirdest spec. I've ever read, but that last sentence pretty much sums things up for us. We will coat the fasteners after installation to mitigate corrosion concerns. The product is designed to meet ASME B31 standards, and will be shipped overseas. My service tech doesn't relish the thought of travelling to BF East Asia to replace some cap screws.
RE: ASTM F1941 - zinc plating high-strength cap screws?
I don't have access to it at the moment, so I can't give you the number.
RE: ASTM F1941 - zinc plating high-strength cap screws?
RE: ASTM F1941 - zinc plating high-strength cap screws?
It's one of the standards that included in the SAE Fastener Standards Manual, HS-4000 if you have that book handy.
RE: ASTM F1941 - zinc plating high-strength cap screws?
There is only a very brief mention of hydrogen embrittlement related to black oxide coatings in SAE J1648. It appears in Table 1 under Description and Requirements. The following is an excerpt:
Porous thin; hydrogen embrittlement susceptible; oiling may be necessary.
SAE AMS 2485 Coating, Black Oxide includes a section that requires inspecting parts for surface and intergranular attack after the coating process. The following is an excerpt:
4.2.2 Periodic Tests: Surface and Intergranular attack (3.3.4) when parts 36 HRC or higher are being processed, and tests of cleaning and coating baths (See 8.2) to ensure that coatings will conform to specified requirements are periodic tests and shall be performed at a frequency selected by the processor unless frequency is specified by the purchaser.
RE: ASTM F1941 - zinc plating high-strength cap screws?