From Wikipedia -
"If the metal has not yet started to crack, hydrogen embrittlement can be reversed by removing the hydrogen source and causing the hydrogen within the metal to diffuse out through heat treatment.
[18] This de-embrittlement process, known as "baking", is used to overcome the weaknesses of methods such as electroplating which introduce hydrogen to the metal, but is not always entirely effective because a sufficient time and temperature must be reached.
[19] Tests such as ASTM F1624 can be used to rapidly identify the minimum baking time (by testing using
design of experiments, a relatively low number of samples can be used to pinpoint this value). Then the same test can be used as a quality control check to evaluate if baking was sufficient on a per-batch basis."
19. Federal Engineering and Design Support.
"Embrittlement" (PDF).
Fastenal. Fastenal Company Engineering Department. Retrieved 9 May 2015.
From reference 19 - "ASTM F1941 has a hydrogen embrittlement relief requirement for coated fasteners made from steel heat treated to a hardness of HRC 40 or above, case hardened fasteners, and fasteners with captive washers (SEM screws) made from hardened steel. The exact time and temperature of the bake is not specified, but times between 2 and 24 hours at temperatures between 350 and 450°F are listed as suitable depending on type, size of fastener, geometry and other variables. "
I'll look around some more. brb