Using un-reactive 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.

Acid fumes from burning coal and oil dissolve in rain water to make acid rain. Acid rain causes lots of damage by corroding metals. Metals first lose their shiny surface, then, as more is removed, they lose their strength. 

Metal corrosion is a big problem. It is most serious for the metals at the top of the interactivity 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 un-reactive 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 can.

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.