Question

I have a few questions I need answered about Corrosion:

1) How does a polymer (plastic) coating protect steel from rusting?

2) How does Galvanization (zinc-plating) protect steel from rusting?

3) How does paint protect a car from rust?

4) Why do people waz their vehicles when they wash them?

5) How does magnesium protect zinc from oxidization?

6) What is meant by sacrifcial electrode?

Answer 1

1) How does a polymer (plastic) coating protect steel from rusting?

answer : plastic can act as barrier in between iron and atmosphere. that means atmospheric oxygen and mositure cannot reach the iron . so iron is protected from corrosion this is called barrier protection

2) How does Galvanization (zinc-plating) protect steel from rusting

answer : one thing we have to remember . the rusting of iron is due to oxidation reaction of Iron.

Fe ----------------------------> Fe+2 + 2e-

if we stop this reaction steel can be protected . for this galvanization process is used

in the galvanization process Zn metal is used . because the reduction potential of Zn is less than that of Fe. so first Zn oxidise to form Zn+2 insted of iron oxidation.

3) How does paint protect a car from rust?

paints also barrier between metal and atmosphere so we can prevent corrosion

5) How does magnesium protect zinc from oxidization?

Mg reduction potential is less than Fe and also more reactive metal . when we add Mg metal to Fe so we protect ion

because Mg is oxidised instead of Fe. that means Mg is sacrificial metal to protect iron

Mg------------------> Mg+2 + 2e-   , E(o) = -2.38 V

Fe+2 + 2e - -------------------> Fe (s) , E(o) = -0.44

whenever Fe converts into Fe +2 it is again convert as Fe by means of Mg .

this is called sacrifcial protection . here Mg electrode is sacrifcial electrode

6) What is meant by sacrifcial electrode

same 5th answer

note : 4th question i do not understand