What are non-ferrous metals and alloys, why are they chosen over steel, and where do aluminium, copper, brass and their relatives belong in engineering?
Describe the composition, properties and applications of non-ferrous metals and alloys, including aluminium, copper, brass and bronze, and select appropriate non-ferrous metals for engineering tasks
A focused guide to non-ferrous metals for HSC Industrial Technology Metal and Engineering. What makes a metal non-ferrous, the properties and uses of aluminium, copper, zinc, lead and titanium, common alloys such as brass and bronze, and how to select them.
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What this dot point is asking
Non-ferrous metals are everything that is not based on iron, and they solve problems steel cannot, such as light weight, corrosion resistance and electrical conductivity. NESA expects you to describe the composition, properties and applications of the main non-ferrous metals and alloys, and to select them for engineering tasks. This sits alongside ferrous metals as core material knowledge for the focus area, examined in the written paper and applied in your Major Project.
What makes a metal non-ferrous
A non-ferrous metal contains little or no iron. As a group they tend to be non-magnetic and to resist corrosion far better than plain steel, which makes them valuable where rust, weight or conductivity matter. They are generally more expensive than carbon steel, so they are chosen for a specific property rather than as a default material.
The main non-ferrous metals
- Aluminium: very light, corrosion-resistant thanks to a self-forming oxide layer, a good conductor and easy to machine and extrude. Used in frames, transport, cookware and structures where weight matters. It is soft in pure form and harder to weld than steel.
- Copper: an outstanding conductor of heat and electricity, ductile and corrosion-resistant. Used in wiring, plumbing and heat exchangers.
- Zinc: corrosion-resistant and used mainly to galvanise steel and in die-casting.
- Lead: heavy, soft, dense and corrosion-resistant, used for shielding and weatherproofing, though its toxicity limits modern use.
- Titanium: light, very strong and highly corrosion-resistant, used in aerospace and medical work where its high cost is justified.
Alloys of non-ferrous metals
Alloying combines metals to get properties no single metal has:
- Brass: copper alloyed with zinc. Stronger and harder than copper, attractive, corrosion-resistant and easy to machine, used for fittings, decorative work and instruments.
- Bronze: copper alloyed with tin. Hard, tough and very corrosion-resistant, used for bearings, marine fittings and statuary.
- Aluminium alloys: aluminium with elements such as copper, magnesium or silicon, much stronger than pure aluminium and used structurally in transport and construction.
Properties that drive selection
Non-ferrous metals are usually chosen because steel cannot do the job:
- Light weight: aluminium and titanium where mass must be minimised.
- Corrosion resistance: most non-ferrous metals for marine, outdoor or hygienic use.
- Conductivity: copper and aluminium for electrical and thermal work.
- Appearance: brass and bronze for decorative and architectural pieces.
The trade-offs are higher cost, lower strength than steel in some cases, and often greater difficulty in welding.
Selecting a non-ferrous metal
Match the metal to the demand. Use aluminium where weight and corrosion resistance matter, copper where conductivity is needed, brass for machined fittings and decorative work, bronze for marine bearings, and titanium where light weight and strength justify the cost. State the property driving the choice and weigh it against the higher price compared with steel, because that reasoning is what earns marks and what guides a sound Major Project material decision.
Exam-style practice questions
Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
2021 HSC1 marksWhat is alloyed with copper to form bronze? A. Iron B. Tin C. Tungsten D. ZincShow worked answer →
The correct answer is B: tin.
Bronze is an alloy of copper and tin. Adding tin to copper produces a metal that is harder and stronger than pure copper while keeping good corrosion resistance, which is why bronze is used for bearings, marine fittings and bells.
Copper alloyed with zinc (D) gives brass, not bronze, so D is the common distractor. Iron (A) and tungsten (C) are not the alloying element used to make bronze, so B is correct.
2019 HSC1 marksWhich combination of metals makes brass? A. Copper and tin B. Copper and zinc C. Tin and manganese D. Manganese and zincShow worked answer →
The correct answer is B: copper and zinc.
Brass is an alloy of copper and zinc. Varying the proportion of zinc changes the colour, strength and machinability, which is why brass is used for fittings, fasteners and decorative work.
Copper and tin (A) makes bronze, not brass, so A is the classic distractor in this pairing. The combinations involving manganese (C, D) are not the standard recipe for brass, so B is correct.
2021 HSC2 marksOutline the properties of copper that make it ideal for electrical wiring.Show worked answer →
Award up to two marks for outlining the relevant properties and linking them to electrical use.
High electrical conductivity. Copper is one of the best conductors of electricity after silver, so it carries current with very low resistance and minimal energy loss as heat, which is the primary reason it is chosen for wiring.
Ductility and corrosion resistance. Copper is highly ductile, so it can be drawn into long, thin, flexible wires without breaking, and it resists corrosion and oxidation, giving reliable long-term connections. These properties together make it the standard material for electrical wiring.
2021 HSC4 marksDescribe the process to produce aluminium from its raw materials.Show worked answer →
A four-mark answer should describe the main stages from ore to metal.
Mining and refining. Aluminium is extracted from bauxite ore. The bauxite is refined using the Bayer process, where it is crushed and treated with hot caustic soda to dissolve the alumina and separate it from impurities, producing pure alumina (aluminium oxide).
Smelting. The alumina is then reduced to aluminium metal by electrolysis in the Hall-Heroult process. The alumina is dissolved in molten cryolite in large reduction cells and a very large electric current is passed through it.
Separation and casting. The electrolysis splits the alumina so that molten aluminium collects at the cathode at the bottom of the cell, where it is siphoned off. The molten metal is then cast into ingots for use. The process is very energy intensive, which is why recycling aluminium is so important.