Metallic materials¶

They are materials that are obtained by heating minerals in a furnace, generally metal oxides and sulfides, obtained in mines.

Index of contents

Properties of metals
periodic table of elements
Alloys
Classification of metals
Ferrous metal
Copper and its alloys
light metals
Heavy metals
noble metals
Metal prices
Unit questions
Questionnaires

Properties of metals ¶

Although different metals have very different properties, there are some properties common to all of them.

Mechanical strength

The mechanical resistance of most metals is very high. Better than the rest of the materials. This is the reason why they are used to make structures. For example, buildings, airplanes, cars, ships, etc.

Malleability and Ductility

Most metals are very malleable and very ductile, which makes it very easy to make thin sheets and cables with them.

Density of metals

It is very variable, but in general they are much denser than water.

Metal	Density (kg/liter)
Magnesium	1.7
Aluminum	2.7
Titanium	4.5
Iron	7.9
Copper	9.0
Lead	11.3
Mercury	13.5
Gold	19.3

Conductivity

Metals are good conductors of heat and electricity.

Oxidation

There are metals, like iron, that rust non-stop until corrosion completely destroys them.

Some metals such as aluminum, silver or lead oxidize superficially and lose their metallic shine. That layer of surface oxide protects them by preventing oxidation from progressing. Thus, these metals are resistant to corrosion.

Other metals such as gold, platinum or chrome maintain their metallic shine without superficial oxidation.

Response to light

The metals are opaque and, polished, reflect light well. They have a characteristic shine called "metallic".

Ecological properties

Metals are easily recyclable many times without degrading.

Many metals are inert and do not react with nature, oxidizing very slowly without producing toxins.

Heavy metals are very toxic to the environment.

Other properties

There are liquid metals at room temperature (mercury and gallium) that can be used to make thermometers, fluorescent tubes, etc.

periodic table of elements ¶

Metals make up the majority of the elements represented on the periodic table.

2012rc, CC BY 3.0, via Wikimedia Commons.¶

Alloys ¶

An alloy is a mixture of a metal with another element. Alloys are generally made by melting a metal with other elements so that they combine so that the result has better properties than the products used.

Examples of alloys are bronze (copper and tin), brass (copper and zinc), steel (iron and carbon), stainless steel (iron, carbon and chromium) or duralumin (aluminum and copper).

Most metals are not used in their pure form, but are alloyed with other elements to improve their properties.

Classification of metals ¶

Ferrous metals: composed mainly of iron. They are the most used due to their low price.
Copper and its alloys: Copper, bronze and brass. They are highly appreciated for their good conductivity, mechanical resistance (bronze) and corrosion resistance.
Light metals: mainly aluminum, titanium, magnesium and their alloys. They are very useful for making airplanes, prostheses, mobile phones, light bicycles, etc.
Heavy metals: lead, mercury, arsenic, cadmium, chromium, nickel, tin, zinc. They are very toxic to the environment.
Noble metals: are metals with great resistance to corrosion, which do not rust. Gold, silver, platinum, rhodium, iridium, osmium.
Rare earth metals: neodymium, yttrium, lanthanum, cerium They are used to form alloys, electronic products, high-performance magnets and superconductors.

Ferrous metal ¶

They are those that are mainly made up of iron. Pure iron is a metal with poor mechanical properties, so these are usually improved through alloys.

Its density is relatively high (7.9 kg/liter).

Steel

It is an alloy of iron with carbon (with a percentage less than 2.1% by weight). It is one of the most used metal alloys for all types of products and structures because it is the cheapest metal, with very good mechanical resistance (break load of 50 to 100 kg/mm2) and very tough.

Foundry

It is an alloy of iron with carbon (with a percentage greater than 2.1% by weight). They are more brittle than steel and have a lower melting point. They are more resistant to corrosion and temperature changes than common steels.

They are used, for example, to make manhole covers, stoves and chimneys, water pump casings, etc.

Stainless steel

It is an alloy of iron with chromium (with a percentage greater than 10%). It is very resistant to corrosion and is used in kitchen utensils, cutlery, sinks, pipes, etc.

Ferrite

It is composed of alpha iron pure, dark in appearance. Sometimes it is alloyed with cobalt, nickel, zinc or manganese, which improve its magnetic properties.

Ferrite has magnetic properties so it is used to make transformers, magnets, filters for cables, etc.

Copper and its alloys ¶

Copper

It is a reddish metal that is a very good conductor of heat and electricity.

It is widely used to manufacture cables, pipes, heat exchangers, coins, pigments, etc. It was the first metal used in prehistory, giving its name to the 'Copper Age <https://es.wikipedia.org/wiki/Edad_del_Cobre>`_.

Bronze

Copper and tin alloy (with a percentage between 3% and 20%). It is very resistant to friction and corrosion.

It is used to build musical instruments, boat propellers, or sculptures.

It was the first alloy obtained by humanity and gives its name to the Bronze Age.

Brass

It is an alloy of copper and zinc.

It has a characteristic golden color, similar to gold, which is why it is widely used in decoration and jewelry. It is also used to make locks, latches, doorknobs, faucets, vases, etc.

light metals ¶

Aluminum

It is the most used metal after steel because it is cheap, has low density (2.8 kg/liter) and very good resistance to corrosion. In its pure state it is very soft and has low mechanical resistance, but properly alloyed it greatly increases its mechanical breaking resistance up to 40 kg/mm2.

It is very ductile and malleable and can be extruded very easily.

It is used to make window frames, metal foil, cans, airplanes, electrical cables, etc.

Despite being the most abundant metal in the Earth's crust during the 19th century, its production was so expensive that it was considered an exotic material with an enormous price, higher than that of gold.

Starting in 1900, its production increased without stopping until today. This was due to the invention of chemical techniques (Bayer process) and the application of the dynamo that makes it possible to produce the electricity necessary to insulate aluminum by electrolysis.

Titanium

Es un metal de color gris, de baja densidad (4,5 kg/litro) muy resistente a la corrosión y con buena resistencia mecánica de rotura, semejante a la del acero.

It has the best hardness/density ratio of all metals. It is almost as strong as steel, but with lower density.

Thanks to its properties, it is highly appreciated for building medical prostheses, aerospace machinery, transporting chemical products, etc. White paints and plastics with a very pure color and very good resistance to solar radiation are manufactured with titanium oxide.

Heavy metals ¶

Lead

It is a dark gray metal that melts easily (327ºC).

It is used in welding electronic components, car batteries, anti-radiation shields, pigments, bullets, etc.

Currently, there is a tendency to reduce its use because it is highly polluting. For example, electronic products increasingly use silver-based solders and components to avoid the use of lead.

Mercury

It is a bright silver liquid metal at room temperature.

An attempt is being made to reduce its use as much as possible to avoid the consequences of its toxicity.

It is used to make fluorescent lights, thermometers, amalgam for fillings, batteries, etc.

Tin

It is a shiny white metal. It is very soft and does not rust.

Tinplate is steel covered with a thin layer of tin and is used in cans. Other uses of tin are soldering electronic components, making bronze and glass, pigments, corks on wine bottles, etc.

Zinc

It is a shiny white and soft metal.

It is used, alloyed with copper, to produce brass. You can coat iron pieces in a process called galvanization that prevents them from rusting. It is also found in electric batteries.

Chrome

It is a grayish-white metal, hard, brittle and very resistant to corrosion.

It is used alloyed with steel to make stainless steel. Chrome plating consists of depositing a protective layer of chrome on another material (plastic, other metals, etc.) giving a shiny appearance that does not rust. Other applications are paints, leather tanning, catalysts, etc.

Nickel

It is a white metal with a slight yellow tone.

It is used alloyed with steel to make stainless steel. Copper-nickel alloys are very resistant to corrosion and are used to manufacture marine engines, the chemical industry or mint coins.

Cadmium

It is a bluish white metal.

It is used in rechargeable Nickel-Cadmium batteries to manufacture bearings with low friction and high fatigue resistance.

noble metals ¶

Gold

It is a golden-colored metal, soft, very ductile, very resistant to oxidation and a very good electrical conductor.

Most gold (70%) is used in jewelry or as an investment. Only 10% of gold is used in industrial applications.

It is used to cover electrical contacts that do not rust, electrical cables of chips, light reflector in glasses lenses, etc.

Platinum

It is a grayish white metal.

It is used in jewelry, electrical contacts, fillings, and catalysts.

Rhodium

Silvery white metal.

It is used as a catalyst for nitrous oxides in automobiles and has no substitute. For this reason, its price has risen so much that it is currently the most expensive precious metal, with a price much higher than that of gold.

Metal prices ¶

Hay varias referencias, pero la más prestigiosa es la bolsa de Londres. Estos precios corresponden al cierre en bolsa sobre el metal puro a día 5 de junio de 2024.