Hydrogen Evolution Reaction

Definition - What does Hydrogen Evolution Reaction mean?

A hydrogen evolution reaction is the production of hydrogen through the process of water electrolysis. The evolution of hydrogen is possibly limited and based on the desorbing of molecules coming from the cathode surface.

Hydrogen evolution usually occurs on metals such as:

  • Platinum
  • Copper
  • Iron

Monitoring hydrogen evolution reactions is very important, since a redox reaction could take place during the process of corrosion of alloys and metals.

Corrosionpedia explains Hydrogen Evolution Reaction

Hydrogen ions are often combined after they undergo reduction in their atomic form to generate hydrogen gas, brought about by the electrons found on cathodic areas. Hydrogen reaction on cathodic ares is capable of disturbing the balance between hydroxyl, which is alkaline, and the ions of hydrogen, making the solution more basic or less acidic.

During the process of corrosion, one or more redox reactions can take place. For instance, alloys of iron and chromium can produce a more cathodic reaction on the metal's surface when both the metals undergo oxidation.

In zinc corrosion in hydrochloric solutions, two cathodic reactions can happen: reduction of oxygen and hydrogen evolution reaction. These two processes take up electrons, making the entire zinc corrosion rate heightened as well. When a piece of steel is submerged in hydrochloric acid, strong bubble formation is seen, which makes the metal undergo corrosion very quickly.

Therefore, acidic solutions that are either exposed to air or dissolved in oxygen are much more corrosive than acids that are air-free. The removal of oxygen from solutions that are acidic turn such solutions less caustic. This is one of the typical techniques to eliminate corrosivity in various environments.

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