The effect of substitution of Nb by Mo in Nb₄₀Ti₃₀Ni₃₀was investigated with respect to microstructural features and hydrogen dissolution, diffusion and permeation. As-cast Nb_40−xMo_xTi₃₀Ni₃₀(x = 0, 5, 10) alloys consist of primary bcc-Nb phase and binary eutectic (bcc-Nb + B2-TiNi). The substitution of Nb by Mo reduces the hydrogen solubility in alloys, but may increase (x = 5) or decrease (x = 10) the apparent hydrogen diffusivity and permeability. As-cast Nb₃₅Mo₅Ti₃₀Ni₃₀exhibits a combined enhancement of hydrogen permeability and embrittlement resistance as compared to Nb₄₀Ti₃₀Ni₃₀. This work confirms that Mo is a desirable alloying element in Nb that can contribute to a reduction in hydrogen absorption and an increase in intrinsic hydrogen diffusion, thus improving embrittlement resistance with minimal permeability penalty.

The effect of hydrostatic pressure (HP) on the corrosion behaviour of X80 steel is investigated to assist the development of deep-sea oil and gas resources. The results show that the corrosion current increases as HP increases whereas the charge transfer resistance follows the opposite trend. The corrosion products are composed of γ-FeOOH, α-Fe₂O₃ and α-FeOOH at atmospheric pressure, while Fe₃O₄ is only formed at a high HP. Additionally, the inner layer of the corrosion products contains more Fe₃O₄ compared with the surface corrosion layer. HP accelerates the corrosion rate of X80 steel due to its effect on the chemical and physical properties of the corrosion products, including the promoted reduction of γ-FeOOH and the formation of wider and deeper cracks on the corrosion product layer.