Effect Of Hydrogen Charging Method On Fracture Properties Of 225Cr-Mo(-V) Alloys – Application Of Fracture Mechanics Concepts – Review Of Available Data. For some years conventional 225Cr1Mo grade is less and less used for the fabrication of heavy refining reactors and replaced by 225Cr1MoV grade which offers much better mechanical properties at high temperatures. This change also offers large benefits on hydrogen resistance due to large differences in hydrogen solubility diffusion and trapping behaviour between the two grades.Focusing more deeply on differences between the two previously cited grades it appears that 225Cr1MoV offers an important gain in term of hydrogen resistance but has also a very complex behaviour strongly depending on charging method used to introduce hydrogen in material. Trapping and diffusion behaviours are particularly different when hydrogen is introduced using autoclave charging (gaseous hydrogen as in refining industry) or using sour service environment (aqueous hydrogen sulphide using as in gas treatment industry).This paper proposes to explain the differences between the two previously cited grades when facing gaseous and aqueous hydrogen and then the consequences on fracture performance. This demonstration is based on actual hydrogen diffusion and solubility laws measurements associated to fracture mechanics tests.Keywords: 2.25Cr-1Mo 2.25Cr-1Mo-V Hydrogen Diffusion Hydrogen Solubility Trapping Effect Gaseous Hydrogen Aqueous Hydrogen Fracture Mechanics.