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Nickel - Properties, Fabrication and Applications of Commercially Pure Nickel

Topics Covered

Introduction

Background

Corrosion Resistance

Properties of Commercially Pure Nickel

Fabrication of Nickel

Nickel in Chromium Plating

Introduction

Nickel  (Ni) was discovered in 1751 in Stockholm, Sweden by A.F. Cronstedt. It is a silver-white metal which mainly occurs in the arsenic and sulphide ores. It is extracted by roasting to NiO and then reducing with carbon. The Mond process is used to manufacture pure nickel, where in impure nickel reacts with carbon monoxide (CO) to produce Ni(CO)4, which is subsequently decomposed at 200 °C to yield 99.99% Ni. Nickel has an abundance of 80 ppm in the earth's crust.

Pure nickel is resistant to corrosion in water or air, and therefore is used as a protective coating. It is malleable and ductile and readily soluble in dilute acids, but is not affected by alkalis.

When it comes to applications, nickel is used as a constituent of different types of alloys; for instance, Monel (corrosion resistant material), Nichrome (an alloy used for resistance heating elements), Permalloy (an alloy with high magnetic permeability at low field strength and low hysteresis loss), cupro-nickel, stainless steel, nickel silver, etc.

In addition, nickel is used as a protective coating and within food and chemical handling plants and in coinage.

Nickel is classified as a carcinogen and is also an allergen to certain individuals. However, it is found in many dietary constituents, and hence cannot be avoided easily.

Background

Commercially pure or low alloy nickel finds its main application in chemical processing and electronics.

Corrosion Resistance

Due to its corrosion resistance, particularly to various reducing chemicals and especially to caustic alkalis, nickel is used to maintain product quality in many chemical reactions, particularly the processing of foods and synthetic fibre manufacture.

Properties of Commercially Pure Nickel

Compared to nickel alloys, commercially pure nickel has high electrical conductivity, a high Curie temperature and good magnetostrictive properties. Nickel is used for electronic lead wires, battery components, thyratrons and sparking electrodes.

Nickel also has good thermal conductivity. This means it can be used for heat exchangers in corrosive environments.

Battery components and other elctronic applications use Nickel. Image Credit: Shutterstock/mariva2017

Fabrication of Nickel

Annealed nickel has a low hardness and good ductility. Nickel, like gold, silver and copper, has a relatively low work hardening rate, i.e. it does not tend to become as hard and brittle when it is bent or otherwise deformed as do most other metals. These attributes, combined with good weldability, make the metal easy to fabricate into finished items.

Nickel in Chromium Plating

Nickel is also frequently used as an undercoat in decorative chromium plating. The raw product, such as a brass or zinc casting or a sheet steel pressing is first plated with a layer of nickel approximately 20µm thick. This gives it its corrosion resistance. The final coat is a very thin ‘flash’ (1-2µm) of chromium to give it a colour and tarnish resistance that is generally regarded as more desirable in plated ware. Chromium alone would have unacceptable corrosion resistance because of the generally porous nature of chromium electroplate.

Table 1. Properties of Nickel 200, the commercially pure grade (99.6% Ni).

Property Value
Annealed Tensile Strength at 20 °C 450 MPa
Annealed 0.2% Proof Stress at 20 °C 150 MPa
Elongation (%) 47
Density 8.89 g/cm3
Melting Range 1435-1446 °C
Specific Heat 456 J/kg. °C
Curie Temperature 360 °C
Relative Permeability Initial 110
Maximum 600
Co-Efficient if Expansion (20-100 °C) 13.3x10-6m/m.°C
Thermal Conductivity 70 W/m.°C
Electrical Resistivity 0.096x10-6 ohm.m

Source: Abstracted from Handbook of Engineering Materials, 5th Edition.

For more information on this source please visit The Institute of Materials Engineering Australasia.

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