1       Using Unreactive Metals

The two nails in
the photograph look very different. The top one has been taken
straight from the packet. It is still shiny. The bottom one has been in acid for
a week. The acid has reacted with the iron in the nail and has started to
eat it away. The nail has rusted or corroded.

A
metal corrodes whenever a chemical attacks its surface. Water, air and acid
are three of the most common corroding chemicals. When a piece of metal
corrodes, it first loses its shiny surface. Then, as more and more is
eaten away, it loses its strength.

Metal corrosion
is a big problem. It is most serious for the metals at the top of the
reactivity series. They corrode so rapidly that they are of little use. It is also
serious for less reactive metals like iron. The rusting of iron costs
millions of pounds each year. Only the metals at the bottom of the series
do not suffer from serious corrosion problems. They corrode slowly,
if at all.

Using Unreactive metals

Metals which don't corrode can be very useful.

Gold is used for
making jewellery. It does not corrode and so stays shiny.

Copper is used
in plumbing. Copper pipes and tanks are not corroded by water, and so they don't leak.

Tin is used for coating tin cans. The can is really made out of
steel (which
is mostly iron). This makes the can strong and cheap. The tin protects the
steel from being corroded by the food in the container.

Titanium is a metal which has recently
become important. It is strong and light and is not easily corroded. Most
titanium is used to make aircraft. It is also used for making artificial
hip joints.

1 a) What happens to a piece of metal when it
corrodes':1 A

b) Write down three things which can
make a metal corrode. A

2 a) Where in the activity series are the
metals most affected by

corrosion?  A

b] Name some of
these metals, and some which don't corrode.

3  Why does a 'tin' can have tin and
steel in it? A

4  a) Name some
metals which are used to make jewellery,

b)
Why are these metals used?

5  Why is it
dangerous to drive a car which is really rusty?

6  Try to find
out:    a) why metals
corrode more quickly near the sea

b) why car exhausts rust
so quickly.

Did you know?

• The coins in the picture

came from the wreck of the

Marie Rose. It lay under the

sea for over 400 years.

• Many underwater
craft

(submersibles)
are made of

titanium
because it is so

strong and corrosion

resistant.