19. a) Define corrosion, what name is given to the corrosion of iron ?
b) Name the colour of coating formed on silver and copper articles, when exposed to air?
c) List two damages caused by corrosion and suggest how corrosion can be prevented.
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a) Corrosion is a slow destruction of metal which is caused due to the attack of atmospheric gases such as hydrogen, hydrogen sulphide, carbon dioxide on the surface of metals to convert metals into oxides, carbonates ,etc.Rusting is the name given to corrosion of iron.
b) Silver articles become black after sometime when exposed to air . This is because it reacts with sulphur in the air to form a coating of silver sulphide ( Ag2S ) . 2) Copper reacts with moist carbon dioxide in the air and slowly loses its shiny brown surface and gains a green coating .
c) it's damages:
loss of material
maintenance cost.
we can prevent corrosion by;
Keep the area around the metal surface dry.
Use drying agents and moisture barrier products.
Make sure underground piping is laid in a layer of backfill, such as limestone.
b) Silver articles become black after sometime when exposed to air . This is because it reacts with sulphur in the air to form a coating of silver sulphide ( Ag2S ) . 2) Copper reacts with moist carbon dioxide in the air and slowly loses its shiny brown surface and gains a green coating .
c) it's damages:
loss of material
maintenance cost.
we can prevent corrosion by;
Keep the area around the metal surface dry.
Use drying agents and moisture barrier products.
Make sure underground piping is laid in a layer of backfill, such as limestone.
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