Aluminium and aluminium alloys, like the majority of metals in their liquid state can dissolve significant quantities of gas. The most soluble gas in molten metal is hydrogen. Hydrogen bubbles present in molten metal materialise as porosity during the solidification of the metal. This porosity is harmful to the mechanical properties, sealing and aesthetic appearance of the moulded parts. Aluminium Martigny France has developed three processes which enable the degassing of aluminium and its alloys :1.Chemicalmanual process through addition of degassing tablets such as Desydral N70P or Desydral N71P.2.Chemicalmanual process through injection of a neutral gas (usually Nitrogen) through a degassing air stem closed with a porous plug3.Chemical automatic process through degassing machines such as Rotoxal.