sacrificial protection and galvanising

Question 1

what is galvanising

Answer 1

the coating of a metal with zinc protects the underlying iron in two ways

Question 2

how does galvanising protect iron

Answer 2

1. it prevents oxygen and air getting into contact with the iron
2. it protects by sacrificial protection

Question 3

what is sacrificial protection

Answer 3

when a more reactive metal is placed in contact with a less reactive metal, the more reactive corrodes the other metal first, preventing the corrosion of the less reactive metal

Question 4

sacrificial protection of iron by zinc

Answer 4

if some galvanised iron is scratched, some of the iron surface is exposed and in the presence of water, an electrochemical cell is set up

zinc is more reactive than iron, so it loses electrons more rapidly than iron

the zinc corrodes faster than iron. we say that it is a sacrificial metal

the iron remains protected because the electrons are accepted on the surface keeping it in a reduced state rather than oxidising

the electrons donated by the zinc react with hydrogen in the water to release hydrogen gas