What is the advantage of using ASTM A182 F5 over SS316 for line containing Hydrocarbons with H2S and sulphur based hydrocarbon compounds to roughly 3 % at 425 deg C and 3 kg/cm2 pressure In what kind of service is F5 material generally preferred and is it costlier than SS316 Please advise Regards

Steels of type 5Cr-1Mo are characterized for having good resistance to hydrogen attack, good resistance to hot oxidation, resistance to sulphur corrosion, and also to H2S corrosion. The field of use of these steels in oil refineries is destined almost in exclusive to heater pipes in Atmospheric distillation and Vacuum process units. The rate of hot oxidation of the P5 is of 2mm/year at 704-ºC. The temperature limit of use of P5 steel is 621ºC. At 371 ºC, the corrosion rate by the sulphur for the P5, is of 1mm/year In accordance with Nelson curves, for the same partial hydrogen pressure, the limit temperature use of a P9 is significantly superior to the one of P5 steel. Although the P9 presents weak resistance to napht%E9nic acid corrosion, still so, because of its chromium and molybdenum contents (9Cr and 1 Mo) this type of steel, comparatively to the P5, has bigger resistance to naphtenic acid corrosion.