Difference between Hastelloy G30 /C276 alloy - Knowledge

The core difference between Hastelloy G30 and C276 lies in their chemical composition design, which leads to distinct advantages in corrosion resistance scenarios and slight differences in mechanical properties. Hastelloy G30 is optimized for mixed acid environments, while Hastelloy C276 excels in strong oxidizing and reducing acid environments.

1. Chemical Composition Differences

The key distinction lies in the content of chromium (Cr), copper (Cu), molybdenum (Mo), and tungsten (W). These elements directly determine their corrosion resistance mechanisms.

Element	Hastelloy G30 (UNS N06030)	Hastelloy C276 (UNS N10276)	Core Role of the Element
Chromium (Cr)	28.0 – 31.0%	14.5 – 16.5%	Enhances oxidation resistance; forms dense Cr₂O₃ film.
Copper (Cu)	1.0 – 2.4%	≤ 0.08% (trace)	Improves resistance to sulfuric acid and hydrochloric acid.
Molybdenum (Mo)	4.0 – 6.0%	15.0 – 17.0%	Enhances resistance to reducing acids (e.g., hydrochloric acid); inhibits pitting corrosion.
Tungsten (W)	1.5 – 4.0%	3.0 – 4.5%	Cooperates with Mo to improve resistance to localized corrosion (e.g., crevice corrosion).
Nickel (Ni)	Balance	Balance	Base metal; ensures alloy ductility and stability.

Key Summary:

Hastelloy G30 has higher Cr content (≈30%) and added Cu, which are tailored for mixed acid corrosion.

Hastelloy C276 has higher Mo content (≈16%) and no intentional Cu addition, focusing on all-round corrosion resistance in strong acids.

2. Corrosion Resistance Differences

This is the most critical difference between the two grades, as their composition designs target different corrosive environments.

Hastelloy G30: Superior in Mixed Acid Environments

Optimal for "mixed acid" scenarios: It performs best in environments containing a combination of sulfuric acid, nitric acid, and hydrochloric acid. This is common in chemical processes such as fertilizer production and metal pickling.

Excellent resistance to sulfuric acid: The added Cu and high Cr content work together to resist corrosion from medium-to-high concentration sulfuric acid (especially at 60–90°C).

Good resistance to nitric acid: The high Cr content (≈30%) provides strong oxidation resistance, making it suitable for dilute-to-concentrated nitric acid environments.

Hastelloy C276: All-Round in Strong Oxidizing/Reducing Acids

Strong resistance to reducing acids: The high Mo content (≈16%) makes it highly resistant to strong reducing acids like hydrochloric acid, even at high temperatures and concentrations.

Good resistance to oxidizing acids: It can withstand dilute nitric acid, chromic acid, and organic acids (e.g., acetic acid). However, its lower Cr content (≈15%) makes it less effective than G30 in concentrated nitric acid or mixed acids with high nitric acid content.

Excellent resistance to localized corrosion: The combination of Mo and W gives it outstanding resistance to pitting corrosion and crevice corrosion in chloride-containing environments (e.g., seawater, brine).

3. Mechanical Property Differences

The two grades have similar mechanical properties at room temperature, but there are slight variations due to composition differences, especially at elevated temperatures.

Property	Hastelloy G30 (Room Temp)	Hastelloy C276 (Room Temp)
0.2% Offset Yield Strength	≥ 310 MPa	≥ 310 MPa
Ultimate Tensile Strength	≥ 760 MPa	≥ 795 MPa
Elongation (%)	≥ 40%	≥ 40%

Key Note:

At elevated temperatures (above 600°C), Hastelloy G30 has slightly higher tensile strength due to its higher Cr content, which enhances high-temperature structural stability.

Hastelloy C276 has better creep resistance (resistance to long-term deformation under high temperature and stress) because of its higher Mo content.

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4. Typical Application Differences

Their application fields are clearly divided based on corrosion resistance advantages.

Hastelloy G30 Applications

Chemical industry: Equipment for producing mixed acids (sulfuric acid + nitric acid + hydrochloric acid), such as reactors and heat exchangers.

Fertilizer industry: Components in phosphate fertilizer production (resisting corrosion from phosphoric acid and sulfuric acid mixtures).

Metal processing: Pickling tanks and pipelines for stainless steel and titanium alloy pickling.

Hastelloy C276 Applications

Petrochemical industry: Equipment for processing sour crude oil (resisting H₂S, chloride, and organic acid corrosion), such as oil well pipes and separators.

Pharmaceutical industry: Reactors and pipelines for producing drugs using strong acids (e.g., hydrochloric acid, acetic acid).

Marine engineering: Components in seawater desalination plants (resisting chloride-induced pitting corrosion).