Corrosion & its Control

Rusting is a ------- process.

• mechanical

• physical

• chemical

• thermal

Chemical formula of rust is

• FeSO₄

• FeS

• FeCl₂

• Fe₂O₃.xH₂O

During rusting of iron, reaction occurring at cathode is

• 2 Fe (s)→2 Fe²⁺ + 4 e

• O₂(g) + 4 H⁺(aq) + 4 e ⎯→ 2 H₂O (l )

• 2 Zn (s)→2 Zn²⁺ + 4 e

• 2 Cu (s)→2 Cu²⁺ + 4 e

Corrosion can be prevented by

• Alloying with other elements

• Dehumidification of environment

• Cathodic protection

• All of the above

Select the WRONG statement

• Dry corrosion occurs rarely

• Wet corrosion is called immersed corrosion

• Wet corrosion takes place by adsorption mechanism

• Dry corrosion occurs in the absence of moisture

Metal used to protect iron by cathodic protection

• Ag

• Cu

• Sn

• Zn

Agents responsible for rusting of iron

• water

• oxygen

• water & oxygen

• oil

Ratio of metal oxide formed to metal consumed is called standard volume ratio.

• true

• false

Higher the position of the metal in the galvanic series---------- is the corrosion

• greater

• lesser

• not affected

Zinc & magnesium function as------ w.r.t. protection of iron

• cathode

• anode

• alloying metals

• sacrificial anodes