Hydrogen Embrittlement Relief: Understanding the Phenomenon and Prevention

There are many different phenomena and challenges that come with any type of plating or finishing process. One of the ones that we often encounter is hydrogen embrittlement. This unique but damaging process involves the introduction of hydrogen to a metal being worked on in some way, such as plating or welding. These atoms cause the microstructure of the metal to become far more brittle, and as the metal cools or encounters particularly cold temperatures, it then can experience cracking. However, hydrogen embrittlement can easily be avoided if you understand how it works!

So what is hydrogen embrittlement?

Every metal is made up of a regularly patterned microstructure of atoms, and this structure is what gives the metal its properties. Things like high strength, hardness level, and other structural and physical properties are all thanks to that neat and tidy structure that makes up the metal. During certain processes though, like welding, plating, and manufacturing, as well as in specific environments, there is the potential for hydrogen to get introduced into that microstructure. 

Hydrogen gas consists of molecules each made of two strongly-connected hydrogen ions, and typically those bonds are strong and incredibly difficult to break. But as temperatures rise, say during a welding operation, or if there are certain chemicals involved, those bonds break down, resulting in free hydrogen ions–and these are much smaller and more flexible than the molecules. These ions can diffuse into the microstructure of the exposed metal, causing the bonds to weaken as they are absorbed within it and making the metal far more brittle. When temperatures reach a critical low point, the microstructure will start to break down, which causes the metal to crack. 

How Hydrogen Embrittlement can be prevented

There are many ways to prevent this phenomenon, with the main one being to simply minimize the exposure of the metal to any sources of atomic hydrogen. These include corrosive conditions and environments, where hydrogen gas or ions are more prevalent. Coating and finishing operations are also an excellent way to prevent hydrogen embrittlement, especially for parts that will have to encounter corrosive conditions. 

However, if diffusion of hydrogen into the material is likely to occur regardless of prevention measures, there is a fairly simple way to remove those ions before the metal can be exposed to conditions that would cause it to crack. In the process of hydrogen embrittlement relief or more simply ‘baking’, the metal is put in an industrial oven and heated to and held at a specific high temperature for a set amount of time. These high temperatures allow the hydrogen ions to move much faster and escape the metal, returning the metal’s structure back to its original strength.

Pre- and post-baking operations both have excellent benefits for improving and strengthening metal, though post-baking is most common for hydrogen embrittlement relief. For instance, Reid often performs this service after electroplating operations, which can introduce hydrogen into the metals we treat. This way, our customers can be sure that they’re getting the best quality from our finishing services. 

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