Hydrogen Embrittlement

Last update: Jan 13, 2017

Hydrogen Embrittlement is a form of hydrogen damage stemming from the diffusion of atomic hydrogen into certain types of metals, primarily high strength steels. This embedded hydrogen can then lead to embrittlement, cracking, or catastrophic brittle failure. Hydrogen embrittlement can also have detrimental effects on the ductility and load-bearing capacity of a part. This form of degradation can strike during equipment fabrication, cleaning, repairs, or while in-service.

Hydrogen embrittlement occurs when atomic hydrogen diffuses into certain metals and those metals are later put under applied tensile stresses. The metals that happen to be most vulnerable to hydrogen embrittlement include titanium and titanium alloys, nickel and nickel alloys, aluminum and aluminum alloys, high-strength steels, and low-alloy steels. The metals that are least vulnerable include copper and copper alloys, and austenitic stainless steels, among others.

This diffusion is usually unintentional and can occur during a number of operations. For example during welding, hydrogen can be released from wet electrodes or moisture on the steel. It can affect materials during processes such as applying cathodic protection, pickling, phosphating, or electroplating. Hydrogen can also diffuse into metals during forming or finishing operations. It can diffuse into metal at both low and high temperatures. 

One way to prevent hydrogen embrittlement is to perform a hydrogen bake-out prior to welding or putting metal parts into service. Hydrogen bake-outs drive hydrogen out of equipment and involve heating the metal to an elevated temperature and allowing time for the hydrogen to diffuse out of the steel, leaving it hydrogen-free.

 

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Blog
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