Excellent Corrosion Resistance of Hastelloy C4
Hastelloy C-4 is a nickel-molybdenum-chromium alloy engineered for outstanding resistance to strong oxidizing agents and a wide range of corrosive environments. It demonstrates exceptional stability at high temperatures and superior resistance to stress corrosion cracking, pitting, and intergranular corrosion—making it ideal for use in harsh chemical processing and pollution control systems.
This article introduces the composition, properties, and industrial applications of Hastelloy C-4 to support better material selection in engineering.
What is Hastelloy C4?
Hastelloy C-4 (UNS N06455) is a corrosion-resistant, nickel-based alloy developed to maintain excellent resistance in aggressive chemical environments, particularly at elevated temperatures up to 1040 °C. It offers improved thermal stability and high resistance to chloride-induced stress corrosion cracking compared to earlier Hastelloy grades.
Its unique composition, including a controlled low carbon and silicon content, gives it resistance to grain boundary precipitation in the heat-affected zone, allowing it to be used in welded condition without post-weld heat treatment.
Hastelloy C4 Equivalent Grades
| Standard / System | Equivalent Designation |
| UNS | N06455 |
| ASTM / ASME | ASTM B564, B575, B622, B619 |
| EN / DIN | 2.461 |
| ISO | NiMo16Cr16Ti |
| Trade Name | Hastelloy C-4 (Special Metals) |
Hastelloy C4 Chemical Composition
| Element | Content (%) |
| Nickel (Ni) | Balance |
| Molybdenum (Mo) | 14.0 – 17.0 |
| Chromium (Cr) | 14.5 – 16.5 |
| Iron (Fe) | 4.0 – 7.0 |
| Cobalt (Co) | ≤ 2.0 |
| Carbon (C) | ≤ 0.015 |
| Silicon (Si) | ≤ 0.08 |
| Manganese (Mn) | ≤ 1.0 |
Hastelloy C4 Mechanical Properties
| Tensile Strength | 690 – 760 MPa |
| Yield Strength | ≥ 280 MPa |
| Elongation | ≥ 40% |
| Hardness (HBW) | ≤ 240 |
Hastelloy C4 Physical Properties
| Density | 8.64 g/cm³ |
| Melting Point | 1320 – 1370 °C |
| Thermal Conductivity | ~9.8 W/m·K (at 20 °C) |
| Electrical Resistivity | ~1.2 µΩ·m |
| Modulus of Elasticity | ~205 GPa |
| Service Temperature Range | -196 °C to ~1040 °C |
Applications of Hastelloy C4
- Chemical Processing Plants: Especially in environments containing hot contaminated mineral acids and oxidizing agents.
- Nuclear Waste Reprocessing: Excellent for handling aggressive radioactive solutions.
- Pollution Control Systems: Used in scrubbers, ducts, and stack liners.
- Pulp & Paper Industry: Resists strong bleaching chemicals.
- Pharmaceutical Production: Ensures purity under corrosive chemical exposure.
Advantages of Hastelloy C4
- Excellent resistance to stress corrosion cracking and pitting.
- Superior thermal stability at elevated temperatures.
- High weldability and resistance to intergranular attack post-welding.
- Performs well in both oxidizing and reducing environments.
- Non-magnetic and suitable for sensitive industrial systems.
Limitations of Hastelloy C4
- High material cost due to its nickel and molybdenum content.
- Limited availability compared to more common stainless steels.
- Work hardens rapidly and may require specialized machining techniques.
- Not ideal for environments with high fluoride ion concentration.
Hastelloy C4 vs Other Alloys
| Feature | 316L | 904L | Hastelloy C-4 |
| PREN (Pitting Index) | ~25 | ~35 | ~48–50 |
| Molybdenum Content | ~2% | ~4.5% | ~16% |
| Chloride Resistance | Moderate | High | Excellent |
| Temperature Stability | Limited | Moderate | Very High |
| Cost | Low | High | Very High |
FAQ About Hastelloy C4
Yes. It has excellent resistance to a wide range of acids, including hydrochloric, sulfuric, and nitric acid, especially in hot and concentrated forms.
It has good resistance to chloride-induced pitting and crevice corrosion, making it suitable for some marine applications, but alloys like C-22 or C-276 are often preferred for prolonged seawater exposure.
Yes, Hastelloy C-4 has good weldability using standard welding techniques (GTAW, GMAW), and it does not require post-weld heat treatment in most cases. It is resistant to grain boundary precipitation in the heat-affected zone.
Summary
This article highlights the superior corrosion resistance, mechanical integrity, and high-temperature performance of Hastelloy C-4. As one of the most reliable nickel alloys for aggressive chemical conditions, Hastelloy C-4 is ideal for critical industrial systems where safety and durability are essential.
MT.BOLTS manufactures and supplies Hastelloy C-4 fasteners, flanges, and components for use in demanding applications across chemical, marine, and energy sectors. Contact our team or visit our website to request a quote or more information.
