I. Core Material Selection Principles

Hydrogen Embrittlement Resistance

Avoid carbon steel and low-alloy steels prone to hydrogen embrittlement (e.g., ASTM A36), as hydrogen diffusion at high pressure (≥1MPa) causes lattice distortion and cracking.

Prioritize materials with low hydrogen solubility and high fracture toughness, compliant with ISO 15848-1 (Hydrogen Service Components) and NACE MR0175.

Corrosion and Erosion Resistance

For acidic environments (e.g., H₂S-containing hydrogen), select materials with passivating oxide layers (e.g., stainless steels, nickel-based alloys).

In high-velocity flow sections (nozzle throats, diffusers), use wear-resistant materials to withstand particle erosion (e.g., from catalyst fines in reforming units).

II. Common Materials and Applications

Austenitic Stainless Steels

316L (UNS S31603)

Application Scenarios: General hydrogen service (≤400°C, ≤10MPa), including hydrogen generation via steam methane reforming (SMR) and water electrolysis.

Advantages: Excellent corrosion resistance (against Cl⁻, H₂S), low hydrogen permeability (permeation rate ≤1×10⁻⁷ cm³/(cm·s·Pa)), and good weldability.

Surface Treatment: Electropolishing (Ra ≤0.8μm) to reduce hydrogen adsorption and improve flow efficiency.

304L (UNS S30403)

Suitable for: Low-pressure hydrogen systems (≤2MPa) and non-corrosive media, such as hydrogen purification sections in PEM electrolysis.

Limitations: Lower corrosion resistance than 316L; not recommended for H₂S-containing environments (H₂S concentration >10ppm).

Nickel-Based Alloys

Hastelloy C-276 (UNS N10276)

Key Applications: High-temperature, high-corrosion environments (e.g., sour hydrogen with H₂S ≥100ppm, temperatures ≤150°C).

Technical Features: Resistance to pitting and crevice corrosion in strong acids (e.g., HCl, H₂SO₄), and excellent hydrogen embrittlement resistance even at pressures ≥20MPa.

典型案例: Ejectors in refinery hydrogen plants treating sour gases.

Inconel 625 (UNS N06625)

Used in: High-temperature hydrogen systems (≤650°C), such as ejectors in advanced gasification-based hydrogen production.

Advantages: Maintains mechanical strength at elevated temperatures, with a tensile strength ≥760MPa at 500°C.

Duplex Stainless Steels

2205 (UNS S31803/S32205)

Application Scope: Moderate-pressure hydrogen systems (2–5MPa) with chloride exposure (Cl⁻ ≤1000ppm), e.g., ejectors in seawater-based electrolysis plants.

Composite Advantages: Higher strength than austenitic steels (yield strength ≥450MPa) and better stress corrosion cracking resistance.

Specialized Coatings and Linings

Tungsten Carbide (WC) Coatings

Applied to: Nozzle throats and diffuser walls in high-velocity flow areas (fluid velocity ≥100m/s) to resist erosion from catalyst particles or water droplets.

Coating Methods: Plasma spraying (thickness 0.2–0.5mm), with a hardness of HRC 85–90, extending service life by 3–5 times.

PTFE (Polytetrafluoroethylene) Linings

Suitable for: Low-pressure hydrogen systems (≤1MPa) requiring chemical inertness, such as ejectors in pharmaceutical-grade hydrogen production.

Performance: Excellent corrosion resistance (against all common chemicals), but limited to temperatures ≤260°C and pressures ≤2MPa due to low mechanical strength.