HASTELLOY
Hastelloy G-35 Sheet
Exceptional resistance to phosphoric acid and mixed corrosive environments at elevated temperatures
Hastelloy G-35 is uniquely formulated for applications involving phosphoric acid and other aggressive, complex corrosive environments where temperature and concentration variations demand extraordinary corrosion resistance. The alloy's superior creep strength and thermal stability make it ideal for equipment experiencing sustained exposure above 1200°F.
Quick Specifications
- Density
- 8.33 g/cm³ (0.301 lb/in³)
- Melting Point
- 2400-2500°F (1315-1371°C)
- Yield Strength (0.2% offset)
- 50-65 ksi (345-448 MPa) at room temperature
- Tensile Strength
- 90-110 ksi (621-758 MPa) at room temperature
- Elongation
- 25-35% in 2 inches
- Modulus of Elasticity
- 31.0 × 10⁶ psi (214 GPa) at 70°F
Standards & Certifications
Product Description
Hastelloy G-35 is a highly specialized nickel-iron-chromium-molybdenum alloy engineered specifically for the unique corrosion challenges posed by phosphoric acid processing. Unlike generalist high-performance alloys that excel across many environments, G-35 represents a precision-engineered solution optimized for the complex chemistry of phosphoric acid manufacture, where temperature, concentration, and impurity content all vary significantly during normal operation. The alloy's composition balances exceptional resistance to both dilute and concentrated phosphoric acid with outstanding creep strength that enables reliable service at temperatures exceeding 1200°F—a combination unmatched by competing materials.
The metallurgical structure of Hastelloy G-35 is optimized to resist the particular attack mechanisms that cause premature failure in conventional materials. Phosphoric acid is deceptively corrosive despite appearing less aggressive than hydrochloric or sulfuric acids; the acid's oxidizing power fluctuates based on dissolved oxygen, ferric ion concentration, and temperature—creating conditions that stress the stability of conventional passive oxide films. G-35's sophisticated composition provides passivity stability across these varying conditions while the molybdenum content ensures resistance to localized corrosion initiation. The iron and chromium additions provide additional strength and thermal stability without compromising corrosion resistance.
Hastelloy G-35 exhibits outstanding creep rupture strength at elevated temperatures, maintaining adequate strength at 1400°F where most austenitic stainless steels and conventional nickel alloys lose structural integrity. This thermal capability combined with superior phosphoric acid corrosion resistance makes G-35 invaluable for equipment in thermal phosphoric acid plants where heat recovery and process temperature optimization drive higher operating temperatures than historical equipment. The alloy's resistance to impurity-induced corrosion is equally exceptional; the presence of ferric ions, arsenic compounds, and silica in industrial phosphoric acid processes creates localized corrosion risks that G-35 uniquely resists.
Applications for Hastelloy G-35 concentrate on phosphoric acid processing and related industries where few alternative materials can provide equivalent reliability and service life. The combination of specialized corrosion resistance, exceptional creep strength, and proven long-term performance in some of the world's most hostile chemical environments makes G-35 an essential material for process engineers committed to maximizing productivity while minimizing equipment replacement costs and production interruptions.
Specifications
| Density | 8.33 g/cm³ (0.301 lb/in³) |
| Melting Point | 2400-2500°F (1315-1371°C) |
| Yield Strength (0.2% offset) | 50-65 ksi (345-448 MPa) at room temperature |
| Tensile Strength | 90-110 ksi (621-758 MPa) at room temperature |
| Elongation | 25-35% in 2 inches |
| Modulus of Elasticity | 31.0 × 10⁶ psi (214 GPa) at 70°F |
| Thermal Conductivity | 7.5 BTU/hr·ft·°F at 212°F (13.0 W/m·K) |
| Coefficient of Thermal Expansion | 8.2 × 10⁻⁶ in/in·°F (14.8 × 10⁻⁶ m/m·°C) 68-212°F |
| Creep Rupture Strength (10,000 hrs @ 1400°F) | 12 ksi (83 MPa) |
| Hardness (Annealed) | ≤ 250 HB |
Chemical Composition
| Element | Content (%) |
|---|---|
| Nickel (Ni) | Balance |
| Iron (Fe) | 15.0-20.0 |
| Chromium (Cr) | 22.0-24.0 |
| Molybdenum (Mo) | 6.0-7.5 |
| Tungsten (W) | 2.0-3.0 |
| Cobalt (Co) | 0.0-1.0 |
| Aluminum (Al) | 0.0-0.5 |
| Titanium (Ti) | 0.0-0.5 |
| Manganese (Mn) | 1.0-2.0 |
| Carbon (C) | 0.05-0.10 |
| Silicon (Si) | 0.5-1.5 |
| Sulfur (S) | ≤ 0.015 |
| Phosphorus (P) | ≤ 0.030 |
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength @ 70°F | 50-65 ksi (345-448 MPa) |
| Tensile Strength @ 70°F | 90-110 ksi (621-758 MPa) |
| Elongation (2 inch gauge) | 25-35% |
| Reduction of Area | 50-65% |
| Impact Strength (Charpy V-notch @ 32°F) | ≥ 85 ft·lbf (115 J) |
| Yield Strength @ 1200°F | 35 ksi (241 MPa) |
| Tensile Strength @ 1200°F | 65 ksi (448 MPa) |
| Creep Rupture Strength (10,000 hrs @ 1400°F) | 12 ksi (83 MPa) |
Key Features & Advantages
Applications
Thermal Phosphoric Acid Plant Equipment
Evaporator tubes, heat exchanger bundles, and distillation column internals in phosphoric acid manufacture using the thermal process. Hastelloy G-35's combination of phosphoric acid resistance and high-temperature creep strength enables reliable operation in heat recovery systems optimized for maximum thermal efficiency.
Wet Phosphoric Acid Processing Equipment
Reactor vessels, digesters, and supporting heat exchange equipment in wet-process phosphoric acid plants. The alloy's resistance to ferric ion-induced localized corrosion and impurity attack ensures reliable long-term performance in the complex chemistry of industrial phosphoric acid production.
High-Temperature Heat Exchangers
Shell-and-tube heat exchangers in thermal processing facilities handling hot phosphoric acid or other aggressive mineral acids. The alloy's superior creep strength enables design optimization and higher operating temperatures compared to conventional materials.
Fertilizer Plant Acid Process Equipment
Equipment in superphosphate and other phosphate-based fertilizer manufacturing processes where concentrated phosphoric acid processing combines with elevated temperatures and variable composition streams. G-35 provides superior reliability and extended service intervals compared to conventional materials.
Industrial Chemical Processing Reactors
Pressure vessels and reactor internals in specialty chemical manufacturing involving phosphoric acid or related corrosive media at elevated temperatures. The alloy's specialized corrosion resistance combined with thermal cycling strength makes it ideal for complex chemical synthesis environments.
Acid Recovery and Recycling Systems
Equipment in industrial operations recovering and recycling phosphoric acid or mixed mineral acids where process temperature and acid concentration fluctuate significantly. Hastelloy G-35 maintains integrity through these dynamic conditions where conventional materials fail prematurely.
Frequently Asked Questions
Why is Hastelloy G-35 specifically engineered for phosphoric acid?
What is the maximum temperature at which Hastelloy G-35 provides adequate creep strength?
How does Hastelloy G-35 perform when trace ferric ions or ferrous ions are present in phosphoric acid?
Is Hastelloy G-35 suitable for strongly oxidizing acids like concentrated nitric acid?
What weld filler material should be used when welding Hastelloy G-35 sheet?
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