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Corrosion Resistance of Nickel and Nickel Alloys

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1.Pure Nickel (Ni): Pure nickel exhibits high strength and plasticity, along with good ductility and malleability. It has a relatively high melting point and good resistance to high-temperature oxidation. The standard electrode potential of nickel is -0.25 V (against hydrogen), which is more negative than copper but more positive than iron, chromium, and aluminum, making it a metal material with relatively high thermodynamic stability. Nickel has a certain passivation ability, with passivation performance better than that of iron. However, the corrosion resistance of nickel in most corrosive media depends on its own thermodynamic stability. Overall, nickel demonstrates good corrosion resistance in non-oxidizing acids, alkaline solutions, and salt solutions.

Here is the table format for the corrosion rate of pure nickel in common corrosive media:

Medium and Concentration Test Temperature (°C) Corrosion Rate (mm/year)
Industrial atmosphere (containing SO2, H2S) Room temperature 0.001~0.004
Marine atmosphere Room temperature 0.0001~0.00013
Rural atmosphere Room temperature 0.00003~0.00018
Natural atmosphere Room temperature < 0.003
CO and air saturated condensate

(30% air, 70% CO)

 120°C 0.22
Seawater Room temperature 0.13
Mine water Room temperature 0.0013~0.16
Alkaline and neutral salt solutions Room temperature 0.013
Acidic salt solutions Room temperature 1.0
Sulfuric acid 1% 20°C < 0.1
Sulfuric acid 10% 20°C 1.12
Hydrochloric acid 5% 20°C 0.20
Hydrochloric acid 30% 20°C 2.0
Phosphoric acid 20% 20°C < 1.0
Hydrogen fluoride (dry) 100°C < 3.0
Hydrogen fluoride (moist) 60°C 0.75
Hydrofluoric acid 6% 60°C 1.8
Hydrofluoric acid 10% 76°C 8.94
Potassium hydroxide solution 10~20°C 0.0025
Sodium hydroxide 20% 80°C 0.558
Sodium hydroxide 74~97% > 100°C < 0.1
Sodium hydroxide 74~97% 500°C < 0.1
2. Nickel-Copper (Ni-Cu) Alloys

Copper is a metal with relatively high thermodynamic stability. The addition of copper can enhance the corrosion resistance of nickel in reducing media, especially in hydrofluoric acid, but it reduces the corrosion resistance of nickel in oxidizing media and its oxidation resistance in air.
The most commonly used nickel-copper corrosion-resistant alloys contain 28% to 34% copper, which is monel 400.

Here’s the translated table on the corrosion rates of Monel 400 in various environments:

Environment Type Corrosion Rate Characteristics
Seawater Environment <0.025 mm/year Exhibits excellent corrosion resistance in stagnant or low-flow seawater.
Hydrofluoric Acid Environment Lower than many other alloys Performs well against hydrofluoric acid and fluoride solutions, especially at room temperature.
Hydrochloric and Sulfuric Acid (non-oxidizing acids) Low Shows good corrosion resistance at low concentrations and room temperature.
Caustic Alkaline Solutions (e.g., Sodium Hydroxide) <0.025 mm/year Good corrosion resistance under moderate to low temperatures; low corrosion rates even at high temperatures.
Oxidizing Acids (Nitric Acid) Higher Relatively poor resistance to oxidizing acids, especially under high temperature or high concentration conditions.
Chlorine and Chloride Environments Low Exhibits excellent corrosion resistance to chlorine and most chloride solutions, especially in neutral or alkaline conditions.
Carbon Dioxide Environment <0.025 mm/year Good corrosion resistance in wet carbon dioxide environments; suitable for oil and gas industry applications.
Ammonia Gas and Ammonia Solutions Very Low Almost unaffected by ammonia gas and ammonia solutions, suitable for industrial equipment handling ammonia.

3.Nickel-Chromium (Ni-Cr) Alloys

Nickel-chromium alloys can be roughly divided into four categories based on their chromium (Cr) content: 15% to 25% Cr, 30% to 35% Cr, approximately 40% Cr, and approximately 50% Cr. To further enhance the alloy’s corrosion resistance, strength, and other properties, elements such as iron (Fe), titanium (Ti), and niobium (Nb) are also added.

The most commonly used nickel-chromium alloys is inconel 600.

Corrosion Resistance Rate of Inconel 600 in Various Environments

Environment Type Medium/Solution Corrosion Rate (mm/year)
Atmospheric Environment Industrial atmosphere, sulfuric acid mist in air < 0.025 mm/year (very low corrosion rate)
Marine atmosphere < 0.01 mm/year
Water Environment Seawater 0.0025 – 0.05 mm/year
Freshwater Extremely low, almost no corrosion
Acidic Solutions 50% sulfuric acid (room temperature) 0.5 – 0.8 mm/year
10% sulfuric acid < 0.1 mm/year
50% phosphoric acid (boiling) < 0.025 mm/year
20% hydrochloric acid 0.13 mm/year
Alkaline Environments 50% sodium hydroxide (boiling) Extremely resistant, almost no corrosion
10% sodium hydroxide (room temperature) < 0.025 mm/year
Fluorides Hydrofluoric acid (room temperature) High corrosion rate, not recommended
Oxidizing Environment High-temperature oxygen-containing environment Excellent oxidation resistance, extremely low corrosion rate
Chloride Environment Chlorine gas environment 0.025 – 0.05 mm/year
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