Hastelloy Alloy Overview

Hastelloy alloys are a family of high-performance, nickel-based alloys known for their excellent resistance to corrosion, particularly in harsh environments that include high-temperature and chemically aggressive conditions. These alloys are primarily composed of nickel, with significant amounts of molybdenum, chromium, and other elements like iron and tungsten. Hastelloy alloys are widely used in industries that require materials capable of withstanding severe chemical environments, such as chemical processing, aerospace, and marine engineering.

Key Hastelloy Alloys: B, C, and C-4

Hastelloy B

Composition: Primarily consists of 65-70% nickel, 28-30% molybdenum, and small amounts of iron and cobalt.
Characteristics:

• Excellent resistance to hydrochloric acid and other reducing acids, making it ideal for environments that involve chlorides or chlorine.
• Highly resistant to stress-corrosion cracking in hydrochloric acid.
• Limited oxidation resistance; not suitable for high-temperature oxidizing environments (above 1,100°F / 593°C).
• Good weldability and fabricability.

Applications:

• Widely used in chemical processing for chlorine handling, including tanks, reactors, piping, and valves.
• Employed in industries handling chlorine, hydrochloric acid, and other strong reducing acids.
• Used in pharmaceutical and food processing environments where exposure to acidic chemicals is frequent.

Hastelloy C

Composition: Contains approximately 56-60% nickel, 20-23% chromium, 13-17% molybdenum, and small amounts of iron and tungsten.
Characteristics:

• Exceptional resistance to a wide range of oxidizing acids, including nitric acid, aqua regia, and phosphoric acid.
• Excellent resistance to chlorides, preventing pitting and crevice corrosion in high-chloride environments.
• Can withstand high temperatures (up to 1,800°F / 982°C) and performs well in high-temperature environments with both oxidizing and reducing conditions.
• Excellent weldability and formability.

Applications:

• Ideal for chemical processing environments exposed to oxidizing acids like aqua regia and nitric acid.
• Used in aerospace for components exposed to high temperatures and corrosive environments.
• Commonly employed in marine environments for equipment exposed to seawater and chlorides.
• Used in pollution control systems and refineries.

Hastelloy C-4

Composition: Contains approximately 50-58% nickel, 15-21% chromium, 12-16% molybdenum, with small amounts of iron, tungsten, and other elements.
Characteristics:

• Superior resistance to pitting, crevice corrosion, and stress-corrosion cracking, particularly in high-chloride environments.
• Excellent resistance to sulfuric acid, phosphoric acid, and acetic acid.
• Performs well in oxidizing environments at temperatures up to 1,800°F (982°C).
• High resistance to hydrogen attack and sulfurous gases at elevated temperatures.
• Excellent weldability and fabricability.

Applications:

• Widely used in chemical processing for reactors, heat exchangers, and piping systems exposed to strong acids like hydrochloric, sulfuric, and phosphoric acids.
• Used in petrochemical applications such as offshore oil and gas platforms and desalination plants, where resistance to chlorides and seawater is essential.
• Ideal for nuclear and power generation applications requiring resistance to high temperatures and corrosion.

Summary

• Hastelloy B excels in environments involving hydrochloric acid and other reducing acids, making it perfect for chlorine handling and chemical reactors.
• Hastelloy C offers superior resistance to a wide variety of oxidizing acids and is widely used in chemical processing, aerospace, and marine applications.
• Hastelloy C-4 provides exceptional resistance to pitting and stress-corrosion cracking, particularly in high-chloride environments, making it ideal for chemical processing, oil and gas, and nuclear applications.

Each of these Hastelloy alloys offers unique corrosion resistance and high-temperature stability, making them essential for demanding industrial applications where performance under extreme conditions is crucial.