Hydrogen embrittlement is one of the biggest dangers to your metal items that you will face after you have them blackened. Blacking or blackening metal is a process that coats the surface of your metal with a material that makes it black, grey, or dark blue. It’s commonly used for industrial items so that they are no longer shiny, since shiny items can cause fatigue in an industrial setting. The items can be blacked for many different reasons that are simply aesthetic as well. Ideally, the blacking will protect the metal from rust or corrosion. Since the surface will not be exposed to the contaminants that cause rusting and corroding, they will ultimately be protected. However, blacking exposes the metal to a new danger.
Embrittlement occurs when hydrogen atoms are trapped underneath the surface of the metal. Those hydrogen atoms link up with other hydrogen atoms to form hydrogen molecules. Those molecules force themselves between the molecules of metal, which can cause the metal to become brittle or even begin to crack. You are in danger of hydrogen embrittlement if hydrogen becomes trapped underneath the surface of the metal. That means it is a common problem if you’re blacking is a plating process. When the blacking is a plate that goes over the original metal, it can trap hydrogen.
Furthermore, embrittlement is more common when the substance you use to black your metal is an acidic substance. Acidic substances contain more hydrogen atoms than alkaline substances. If you want to prevent hydrogen embrittlement, you need to submerge metal items in an alkaline solution.
Submerging items in a solution makes it less likely that it will embrittle. Also, you need a solution that alters the existing surface of the metal instead of plating over it. If it alters the existing surface, there will not be space for hydrogen atoms to get trapped. Nothing will be laid over the actual surface. Furthermore, the solution you use should be an alkaline solution. Hydrogen is more commonly trapped in acidic solutions; alkaline solutions are bases instead of acids. They contain less hydrogen and are less likely to embrittle your metal.
Hard metals are more likely to embrittle because they are more likely to resist the expansion of hydrogen molecules. A softer metal will be slightly more pliable, so it will be less likely to become brittle. Whether you have a hard metal or a soft metal, submerging it in the solution instead of plating over it can help resist the embrittlement. It will help you create a reliable surface on your metal items without endangering the items. Such a process becomes especially important for industrial applications in which strength and stability could be life-saving.