The amount of Ferrite in stainless steel weld metals can have an influence on a wide range of properties including corrosion resistance, toughness, long term high temperature stability, resistance to hot cracking etc. It is therefore essential for some applications that the ferrite level is controlled within specified limits and that methods are available for checking that specified levels have been achieved. If the ferrite content is too low, then the welded material is susceptible to hot cracking, if the ferrite content is too high, the toughness as well as the corrosion resistance of the steel is then reduced.