Question

Which of the following statements is not correct about rusting of iron?

• A. Coating of iron surface by tin prevents rusting, even if the tin coating is peeling off.
• B. When pH lies above 9 or 10, rusting of iron does not take place.
• C. Dissolved acidic oxides SO₂, NO₂
• D. Rusting of iron is envisaged as setting up of electrochemical cell on the surface of iron object.

Answer 1

The Correct Option is A

To identify the incorrect statement regarding iron rusting, let's analyze each option:

1. Iron surface tin coating prevents rusting even when peeling:

This statement is false. An intact tin coating protects iron from air and water. However, if the coating peels, iron is exposed. Tin is less reactive than iron; exposed iron will then react with water and oxygen, accelerating rust formation under the peeled areas. Therefore, a peeling tin coating offers no protection.

1. Rusting does not occur at pH above 9 or 10:

This statement is true. At high pH levels, a higher concentration of hydroxide ions (OH⁻) inhibits rusting by forming protective layers on the iron surface, preventing corrosion.

1. Dissolved acidic oxides (SO₂, NO₂) in water catalyze rusting:

This statement is true. These oxides, when dissolved in water, form acidic solutions that accelerate the electrochemical reactions of rusting, acting as catalysts.

1. Rusting is an electrochemical cell formation on the iron surface:

This statement is true. Rusting involves electrochemical reactions where iron acts as the anode and air/water as the cathode, creating an electrochemical cell that promotes iron oxidation.

The incorrect statement is the first one: "Coating of iron surface by tin prevents rusting, even if the tin coating is peeling off."