Degas is often completed prior to welding to pre-existing structures in locations such as refineries, pipelines and other petroleum-based industries, where the structure has been in a high hydrogen concentration environment. Degas refers to the thermal process of removing hydrogen from structures previously exposed to a hydrocarbon environment, where the metal has been compromised by possible hydrogen leaching.
Hydrogen leaching occurs in metals on a molecular level when hydrogen dissociates from its hydrocarbon chain and is then absorbed into the surrounding metal. The high concentration of hydrogen left in the metal after leaching can contribute to hydrogen cracking within the heat-affected zone of the following weld and can lead to structural failure.
