What corrosion protection process would be best to eliminate the possibility of hydrogen embrittlement in 52100 bearing steel? Is zinc nickel a possiblity?
It is useful to separate the effects of hydrogen into two categories: hydrogen that is introduced during steel processing and manufacturing operations (melting & other mill processes, acid pickling, electroplating, etc.) and hydrogen that is introduced during the usage phase of the product (mainly corrosion processes, or actual exposure to liquid/gaseous hydrogen). I believe you are asking about the latter, which is also called Environmental Hydrogen Embrittlement (ASTM F1624) or Environmentally Assisted Cracking (NACE/ASTM G193). Zinc-nickel plating is often used as a corrosion-resistant coating for steel parts, and as such, can be an effective means for reducing or eliminating the possibility of EHE/EAC. However, zinc-nickel is deposited by the electroplating process, which can be a source of hydrogen embrittlement, depending on the exact bath conditions used. Here are two links with good information on the subject:
Effect of Surface Processing Variables and Coating Characteristics on Hydrogen Embrittlement of Steel Fasteners
TVP, Thank you for the links. The dekalbmetal.com article on Zn-Ni was especially helpful.
You are correct; I am talking about hydrogen embrittlement during the usage phase. I have specified in the past that parts which have been electroplated are to be baked at 190 C for at least 3 hours within 4 hours of plating. We have a prospective vendor who uses a hot bath as a post plating treatment. I haven't heard of this before.
52100 is a bearing alloy used for wear resistance at the surface. Why would you put a zinc alloy plating on the surface when it would have no wear resistance? Better options would be nitriding or one of the hard coatings like titanium nitride or diamond like carbon.
The primary function of the 52100 in this application is not wear resistance and the zinc will not be asked to be a wear surface either. It is only for corrosion protection. The 52100 was used simply because it is a standard material for the application and won't affect the product function.
