Overview
Nickel is a silvery-white, ductile, ferromagnetic metal valued as both a pure material and as the base for an extensive family of high-performance alloys (Inconel, Hastelloy, Monel, stainless steels). It provides exceptional corrosion resistance (especially to alkalis and reducing acids), excellent high-temperature properties, and forms a protective oxide. Nickel is a critical strategic metal for aerospace, chemical processing, and battery technology.
Mechanical Properties (Commercial Pure Nickel, annealed)
| Property | Value |
|---|---|
| Density | 8,900 kg/m³ |
| Young's Modulus | 200 GPa |
| Yield Strength | 150 MPa (22,000 psi) |
| Ultimate Tensile | 400 MPa (58,000 psi) |
| Elongation | 40-50% |
| Hardness | 80-120 BHN |
| Melting Point | 1453°C |
| Curie Temperature | 355°C (ferromagnetic below) |
Key Properties
- Corrosion resistance: Excellent in alkaline solutions, reducing acids (non-oxidizing), seawater; resistant to caustic soda up to molten state
- High-temperature performance: Resists oxidation and scaling up to ~1000°C (in alloy form)
- Ductility: Very ductile; easily cold worked, drawn, formed
- Alloying capability: Forms continuous solid solution with copper; basis for hundreds of alloys
- Catalytic properties: Catalyst for hydrogenation reactions (Raney nickel)
- Electroplating: Electrodeposited nickel provides corrosion protection and decorative finish
Major Nickel Alloys
| Alloy | Ni% | Key Elements | Notable For |
|---|---|---|---|
| Nickel 200/201 | 99.6 | — | Commercial pure, food/chemical processing |
| Monel 400 | 66 | 32% Cu | Seawater, HF acid, marine service |
| Inconel 600/625 | 76 | 16% Cr, 8% Fe (625 adds Mo) | High-temperature, oxidation resistance |
| Inconel 718 | 53 | 19% Fe, 18% Cr, Nb+Mo | Precipitation hardening, aerospace |
| Hastelloy C-276 | 57 | 16% Mo, 16% Cr, W | Best corrosion resistance to wide range of acids |
| Hastelloy X | 47 | 22% Cr, 9% Mo, 18% Fe | High-temperature, gas turbine combustors |
Applications
- Chemical processing: Caustic evaporators, reactors, piping for NaOH/KOH service (Nickel 200)
- Aerospace & gas turbines: Inconel 718/X for turbine blades, combustors, discs (high temperature)
- Marine: Monel 400 for seawater piping, shafts, valves, pump shafts
- Stainless steel alloying: Nickel (8%) stabilizes austenitic structure in 304/316 stainless
- Electroplating: Decorative and engineering nickel coatings (often under chrome)
- Batteries: Nickel-metal hydride (NiMH); nickel-cobalt-aluminum (NCA) and NMC in Li-ion batteries
- Catalysts: Raney nickel for hydrogenation; SCR catalysts
- Electronics: Resistors, thermocouples, magnetostrictive materials
Corrosion Performance
- Excellent: Caustic soda (NaOH) up to boiling, most alkalis, seawater, neutral/alkaline salts, food products
- Good: Hydrofluoric acid (Monel is the standard), reducing non-oxidizing acids
- Resistant in alloys: Oxidizing acids (Inconel with Cr), pitting/chloride (Hastelloy C)
- Attacked by: Nitric acid (oxidizing), sulfur-containing atmospheres at high temperature (sulfidation), hypochlorite solutions
Summary
Nickel (density 8900 kg/m³) is far more than a standalone metal — it is the foundation for the entire family of high-performance nickel alloys (Inconel, Hastelloy, Monel) that provide unmatched corrosion and high-temperature resistance. Pure nickel excels in caustic service; its alloys are the go-to choice for extreme environments in chemical processing and aerospace turbines.