Chemical, energy and processing plants are often subject to heat, aggressive media and high pressure.
These circumstances demand steel with high corrosion and acid resistance that are resilient even at high temperatures.
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, ductility as well as the corrosion resistance of the steel are reduced.
It is used a lot to the ferrite content measurement of duplex steel. For duplex steel, a ferrite deficit in the area of the weld seam results in stress corrosion cracking and reduction in strength.