Rusting process. Necessary conditions of Rusting 1.Presence of oxygen (or air) 2.Presence of water

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).