1. Anti-corrosion barrier:

- Excellent performance in strong corrosive environments such as reducing acid (hydrochloric acid, sulfuric acid), oxidizing acid (nitric acid, mixed acid), chloride, seawater, wet chlorine, sulfur-containing medium (H₂S), especially resistant to corrosion in "oxidation-reduction mixed medium" (such as hydrometallurgy, chemical reaction liquid);

- Inhibit pitting, crevice corrosion and stress corrosion cracking (SCC), and its corrosion resistance in chloride solution far exceeds that of ordinary stainless steel (such as 316L).

- High temperature stability:

- Some grades (such as Hastelloy X) can resist oxidation at high temperatures of 1200℃, and most grades still maintain mechanical strength above 600℃, suitable for high temperature corrosion conditions (such as incinerators, flue gas treatment).

2. Alloy system and grade classification

According to the alloy element ratio and performance emphasis, it is mainly divided into the following series (typical grades and characteristics):

1. B series (nickel-molybdenum alloy): focus on reducing acid corrosion (such as hydrochloric acid)

- Hastelloy B-2 (N10665): resistant to hydrochloric acid at any temperature and concentration, and outstanding performance in reduced sulfuric acid and phosphoric acid.

- Hastelloy B-3 (N10675): optimizes thermal stability, has better resistance to intergranular corrosion and pitting than B-2, and is suitable for high-temperature hydrochloric acid environment.

2. C series (nickel-chromium-molybdenum alloy): taking into account oxidation-reduction medium corrosion

- Hastelloy C-276 (N10276): "all-round" alloy, resistant to wet chlorine, hypochlorite, chloride solution and mixed acid corrosion, commonly used in chemical reactors and desulfurization equipment.

- Hastelloy C-22 (N06022): High chromium + molybdenum + tungsten ratio, stronger resistance to local corrosion (pitting, crevice corrosion), suitable for oxidizing media containing chloride ions (such as nitric acid + hydrochloric acid mixture).

- Hastelloy C-2000 (N06200): Adding copper (Cu), the corrosion resistance in sulfuric acid and hydrofluoric acid is improved, and it has both oxidation-reduction environment adaptability.

3. G series (high chromium nickel-based alloy): Focus on phosphoric acid and oxidizing media

- Hastelloy G-30 (N06030): The chromium content is up to 30%, and it has excellent corrosion resistance in wet phosphoric acid, nitric acid + hydrofluoric acid mixture, and is used for phosphoric acid production equipment.

4. X series (high temperature oxidation-resistant alloy)

- Hastelloy X (N06002): Adding cobalt (Co) and tungsten (W), it is resistant to oxidation below 1200℃, and is resistant to neutral/reducing atmospheres. It is used for aircraft engine parts and industrial furnace pipes.

3. Typical application scenarios

1. Chemical and petrochemical industries:

- Pipelines, heat exchangers, and reactors for transporting concentrated hydrochloric acid, sulfuric acid, phosphoric acid, and sodium hypochlorite solutions;

- Transport systems for organic chemical media containing chloride ions (such as vinyl chloride and acetic acid).

2. Oil and natural gas:

- Offshore platform seawater treatment pipelines, sulfur-containing oil and gas (H₂S/CO₂) gathering and transportation pipelines;

- Oil well casings, corrosion-resistant oil pipes (to resist high-salt and high-acid environments downhole).

3. Environmental protection and energy:

- Waste incinerator flue gas pipelines, wet flue gas desulfurization (WFGD) devices;

- Nuclear waste treatment equipment, chemical wastewater pipelines under high temperature and high pressure.

4. Other harsh environments:

- Clean pipelines in the pharmaceutical industry that are exposed to highly corrosive reagents;

- Seawater heat exchangers in marine engineering and coastal power plant pipelines.

4. Manufacturing process and specifications

- Production process:

- Seamless pipe: formed by hot rolling, cold rolling/cold drawing, the tube blank is vacuum melted + electroslag remelted (to ensure purity), and the finished product needs annealing, pickling or polishing;

- Welded pipe: adopts argon arc welding (TIG) or plasma welding, post-weld heat treatment to eliminate stress, and the inner wall has high finish (suitable for clean media).

- Specification range:

- Outer diameter: 6mm~610mm (1/4 inch~24 inches);

- Wall thickness: 0.5mm~50mm (ultra-thin or thick wall tubes can be customized);

- Length: conventional 6m, 12m, or customized length on demand (up to 18m).

5. Implementation standards and quality control

- International standards:

- Seamless pipes: ASTM B622, ASME SB622;

- Welded pipes: ASTM B619/B626, ASME SB619/SB626;

- European standards: EN 2.4602, EN 2.4603, etc. (corresponding grades need to be converted).

- Inspection points:

- Chemical composition analysis (strictly control the content of impurities such as C, Si, S);

- Mechanical properties test (tensile strength, yield strength, elongation);

- Corrosion test (such as ASTM G28 intergranular corrosion test, G48 pitting test).

VII. Selection Recommendations

- If the medium is a reducing acid such as hydrochloric acid or sulfuric acid, the B series is preferred (B-3 is better than B-2);

- If it involves an oxidation-reduction mixed medium (such as mixed acid, wet chlorine), select the C series (C-276 is general, C-22 is more resistant to local corrosion);

- If high-temperature oxidation resistance is required (such as flue gas, heat treatment furnace), select the X series;

- If the medium is phosphoric acid or a strong oxidizing acid, select a high-chromium grade such as G-30.