Properties and Applications of Non-Ferrous Metals
Classification of Non-Ferrous Metals
Non-ferrous metals are classified as heavy, light, and ultralight. Generally, non-ferrous metals are soft and have little mechanical resistance. Their properties improve when alloyed with other metals.
Key Non-Ferrous Metals and Their Properties
Tin
Tin is a relatively scarce metal in the Earth’s crust and is often found in mines. The most exploited tin ore is cassiterite, where tin is found in oxide form. Key characteristics include:
- Pure tin has a bright, silvery color. At ambient temperature, it oxidizes and loses its exterior shine.
- At ambient temperature, it is very malleable and soft; however, when hot, it becomes brittle and fragile.
- Below -18°C, it decomposes in a process called “tin pest.”
- When bent, it produces a rustling sound known as the “cry of tin.”
Copper
The most commonly used copper minerals are native copper, sulfides (chalcocite), and oxides (cuprite). Copper is very ductile (allowing for very fine threads) and malleable (can be formed into sheets). It also has high electrical and thermal conductivity.
Zinc
Zinc has been known since ancient times, but it was not isolated until the 17th century. The primary minerals used in zinc extraction are zinc blende and calamine. Its main features are:
- It is very resistant to oxidation and corrosion in air and water, but it is attacked by acids and salts.
- It has the highest coefficient of thermal expansion of all metals.
- At ambient temperature, it is brittle, but between 100 and 150°C, it becomes very malleable.
Lead
Lead gained importance during the Roman period and from the 19th century onwards. The primary lead ore is galena, which is composed of lead sulfide. Key characteristics include:
- It is malleable and soft.
- It is grayish-white and very bright when freshly cut. It oxidizes easily, forming a protective layer of basic carbonate.
- It resists hydrochloric and sulfuric acids but is attacked by nitric acid and sulfur vapor.
Due to its resistance to atmospheric and chemical agents, lead has many applications, both in pure form and in alloys. Pure lead oxide is used to make paint, coat pipes, and in batteries, and for nuclear radiation protection.
Aluminum
Aluminum is the most abundant metal in nature. It is a component of clay, shale, feldspar, etc. It is not found in a pure state but combined with oxygen and other elements. The ore from which aluminum is obtained is called bauxite, which is composed of alumina and has a reddish color. Its key features are:
- It is very light and stainless in air, forming a thin protective film of aluminum oxide.
- It is a good conductor of electricity and heat. It is often used in electrical wiring because of its low weight.
- It is very malleable and ductile.
Aluminum is normally used in alloys to improve its hardness and strength.
Titanium
Titanium is a component of nearly all volcanic rocks that contain iron. The extraction process is complex, and the minerals from which it is obtained are rutile and ilmenite. Its characteristics are:
- It is a soft, silvery metal that resists oxidation and corrosion better than stainless steel.
- Its mechanical properties are similar to or even higher than those of steel, and it retains these properties up to 400°C.
Due to their low density and high mechanical strength, titanium alloys are used in the manufacture of structures and elements of tuned machines in aviation. To improve its physical properties, it is usually alloyed with chromium and vanadium. It is also used in the manufacture of turbine blades and, in oxide form, in powdered antioxidant paints.
Magnesium (Ultralight Metal)
The most important magnesium sources are carnallite, dolomite, and magnesite. Its properties include:
- In liquid or powder form, it is highly flammable.
- It has a silver-white color.
- It is not very malleable or ductile.
- It is more resistant than aluminum.
Magnesium is commonly used in aeronautics.