Question

Explain how the following protect metals fromcorrosion.

a. paint d. sacrificial metal

b. durable oxide coatings e. alloying

c. galvanizing f. cathodic protection

Short answer

1. Paint prevents the surface of metal from coming in contact with water and air.
2. Chromium and tin form durable oxide coatings on the surface of metal.
3. Zn forms a strong oxide protecting iron from oxidizing.
4. Same as galvanizing, sacrificial metal is more actively oxidized.
5. Nickel and chromium form oxides on the surface of metal and prevent iron from getting oxidized.
6. We keep a metal that is more easily oxidized in electrical contact with the metal we want to protect. The first metal is preferentially oxidized.

Step-by-step solution

Explain how paint protects metals from corrosion

Paint covers the metal surface. This cover prevents the surface of metal from coming in contact with water and air. The surface of metal is safe as long as the surface is not scratched.

Explain how durable oxide coatings protect metals from corrosion

Chromium and tin form durable oxide coatings on the surface of metal. This coating acts as a guard against water and air particles and prevents corrosion.

Explain how galvanizing protects metals from corrosion

Galvanizing is the process of coating steel with zinc. Zn forms a strong oxide coating over steel. Also, zinc is primarily oxidized and prevents iron in the steel from oxidizing.

Explain how sacrificial metal protects metals from corrosion

Sacrificial metal is more actively oxidized. When it is coated on the surface of the metal,it is preferentially oxidized leaving it iron-free and the metal is safe.

Explain how alloying protects metals from corrosion

Chromium and nickelare added to the steel surface. They act as a coating and

prevent iron from getting oxidized. They form oxides on the surface of steel and get preferentially oxidized.

Explain how cathodic protection protects metals from corrosion

In this process, we keep a metal that is more easily oxidized in electrical contact with the metal we want to protect. Hence, the first metal is preferentially oxidized, leaving the second metal safe. In this, the metal we protected becomes the cathode electrode. And so, the process is termed cathodic protection.