Rusting process

Rusting process

Necessary conditions of Rusting

1. Presence of oxygen (or air)2. Presence of water

Rusting process

)oxideiron(III)hydratedvarious(

423

)()(

232

)(232)(232)(232iondecomposit

)(3)(2)()(2)(2)(2)(2

(s)

sss

sOHO

sOHO

s

OxHOFe

OHOFeorOHOFeorOHOFe

OHFeOHFeFe lglg

Rusting process

Conditions that accelerate rusting

1. Presence of a strong electrolyte (e.g. salt solution - a good conductor)

2. Presence of a less reactive metal e.g Sn, Cu3. Presence of acid4. Bent or Sharp angled iron article

The speed of rusting canbe monitored by a yellowrust indicator which will turn blue in the presence of rust (Fe2+

(aq) ion).

Presence of strong electrolyte (e.g. sea water)

Strong electrolyte enhances the conductivity of the solution and speeds up the rusting process.

Presence of less reactive metal (e.g. Sn, Zn) A scratched tin-plated iron can rusts mo

re quickly than an ordinary iron can.

Presence of less reactive metal (e.g. Sn, Cu)

Why does a scratched tin-plated iron can rust more quickly than an ordinary iron can ?

As tin is less reactive than iron, iron will lose electrons through tin at a faster speed than if tin is absent. Therefore, the can will rust more quickly.

Presence of acid

In the presence of acid, Fe(s) forms Fe2+(a

q) ions more readily and rusts faster.

Fe(s) + 2H+(aq) Fe2+

(aq) + H2(g)

Conditions accelerate rusting1. Presence of a strong electrolyte

(e.g. salt solution - a good conductor)2. Presence of a less reactive metal e.g Sn, Cu3. Presence of acid4. Bent or Sharp angled iron article

The speed of rusting canbe monitored by a yellowrust indicator which will turn blue in the presence of rust (Fe2+

(aq) ion).