In galvanisation why does even after the breaking of layer of zinc iron does not get rusted?
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Zinc is more reactive than iron and so will always oxidise before iron. Even if the zinc is just in a large block and iron is fully exposed, it will still oxidise first; this is how sacrificial protection of ships works.
To be oxidised, a metal must lose electrons. Zinc, being more reactive can give up electrons easier than iron can. If an iron atom lost an electron, another would be conducted from the block of zinc to replace it. This will continue until all the zinc has oxidised or unless it is no longer in direct contact.
To be oxidised, a metal must lose electrons. Zinc, being more reactive can give up electrons easier than iron can. If an iron atom lost an electron, another would be conducted from the block of zinc to replace it. This will continue until all the zinc has oxidised or unless it is no longer in direct contact.
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What if the layer of zinc is removed from iron?
The iron will not corrode if it is removed after galvanizing
How? Since zinc is no longer present on the surface of iron
The alkaline medium prevents the availability of H+ions. This in turn reduces rate of oxidation of Fe to Fe2+. Thus, the rusting of iron is inhibited.
Which alkaline medium ?
i) The alkalinity of the solution prevents the availability of H+ ions.
ii) Zinc is more electro positive than iron.
Therefore Zinc coating acts as anode and the exposed iron portions acts as cathode .
If zinc coating is broken ,zinc undergoes corrosion , Protecting iron from rusting. No attack occurs on iron till all the zinc is corroded.
Therefore Zinc coating acts as anode and the exposed iron portions acts as cathode .
If zinc coating is broken ,zinc undergoes corrosion , Protecting iron from rusting. No attack occurs on iron till all the zinc is corroded.
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