Page 54 - Curriculum Visions Dynamic Book

Element
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Manganese Mn)
Chromium (Cr)
Zinc (Zn)
Iron (Fe)
Cadmium (Cd)
Tin (Sn)
Lead (Pb)
Hydrogen (H2)
Copper (Cu)
Mercury (Hg)
Silver (Ag)
Platinum (Pt)
Gold (Au)
(Above) The reactivity series of metals.
amounts in repair bills to ships and other outdoor equipment. It is even used on some cars.
It is important to realise that this only works because the iron is less reactive than the other metal.
If the iron is placed in contact with a less reactive metal, then the iron corrodes very fast. In this example tin and iron are placed together, and the tin remains unaffected. Tin is often used as a protective plating over the iron because it is unreactive; but should the tin plating be damaged, the iron will quickly corrode.
If the water is heated above boiling point (superheated), it will react directly with metals (even when no air is present), and hydrogen gas is given off. Boilers that produce superheated water are therefore liable to become corroded.
In fact, the only metals that do not react with water (either at ordinary temperatures or when
(Below) An iron nail with strips of magnesium (left) and tin (right) attached.
Water containing phenolphthalein indicator shows where electrochemical reactions are taking place.
Over about a week the iron nail is corroded.
Tin strip remains uncorroded.
Iron nail remains uncorroded.
Magnesium strip is corroding within a few minutes.
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