Oxygen, in the thermal-processing atmosphere or bound in surface contamination on the parts, must be reduced to ensure quality results. Chemically reducing atmospheres actively scrub oxygen to enhance results and protect metal
Hydrogen is a widely used reducing agent in thermal-processing atmospheres. Reducing atmospheres generally contain hydrogen (H2) and may contain carbon monoxide (CO) to scrub oxygen. CO may affect metal properties and is poisonous, requiring special care in use. Where hydrogen is the sole reducing agent, it may come from hydrogen delivery, pure hydrogen generation or ammonia dissociation.