“Hydrogen Embrittlement” is a phenomenon that can occur when diffusible hydrogen is introduced to susceptible materials (typically higher strength steels). This can occur in a range of manufacturing operations, including wet electrochemical processes such as electroplating. Hydrogen embrittlement is reversible through a process called “De-embrittlement”, where material is “baked” in an annealing oven at 200° C for several hours.  

We strongly recommend that higher strength steels, particularly high tensile fasteners, are de-embrittled after plating. 

You can learn more here – Hydrogen embrittlement – Wikipedia 

Hydrogen de-embrittlement is the removal of the hydrogen that can be caught between the metal and plating during the process. If you don’t draw it out correctly it can cause the metal to become brittle over time. This process was discovered during WW1 when planes started dropping out of the sky!