CORROSIONCORROSION

Corrosion is a reaction Corrosion is a reaction which takes place on the which takes place on the

surface of a metalsurface of a metal

During corrosion:During corrosion: The metal element changes into a The metal element changes into a

compoundcompound

Magnesium metal + oxygen in air Magnesium metal + oxygen in air

2Mg + O2Mg + O2 2

The metal atoms loose electrons to form The metal atoms loose electrons to form metal ionsmetal ions

Mg Mg

This loss of electrons is called This loss of electrons is called OXIDATIONOXIDATION

Magnesium oxideMagnesium oxide

2MgO2MgO

MgMg2+ 2+ + 2e + 2e--

WHAT IS RUSTING?WHAT IS RUSTING?

The corrosion of iron is called The corrosion of iron is called rustingrusting

For iron to rust you needFor iron to rust you need

a)a) Water (HWater (H22O)O)

b)b) Oxygen from air (OOxygen from air (O22))

2Fe2Fe(s)(s)+2H+2H22OO(l)(l)+ O+ O2 (g) 2 (g) 2Fe2Fe2+2+(aq)(aq)+ 4OH+ 4OH--

(aq) (aq)

The battle against corrosionThe battle against corrosion

MaterialsMaterials BeakerBeaker W tubeW tube 3 nails3 nails Magnesium ribbonMagnesium ribbon Copper ribbonCopper ribbon Ferroxyl indicatorFerroxyl indicator Sodium chlorideSodium chloride

Ferroxyl Ferroxyl indicatorindicator is a pale is a pale yellow-coloured yellow-coloured solution which solution which turns blue when turns blue when FeFe2+2+ ions are ions are produced.produced.

Sodium chlorideSodium chloride (common salt) is (common salt) is an electrolyte, an electrolyte, rusting occurs rusting occurs faster when an faster when an electrolyte is electrolyte is present.present.

ProcedureProcedure

We take three iron nails:We take three iron nails: 1)Nail with Mg ribbon attached to it1)Nail with Mg ribbon attached to it 2)Bare Nail2)Bare Nail 3)Nail with Cu ribbon attached to it3)Nail with Cu ribbon attached to it

We place the nails in the We place the nails in the Sodium chloride solution and we add some drops Sodium chloride solution and we add some drops of of ferroxyl indicator solutionferroxyl indicator solution

What is about to happen?What is about to happen?

1)No 1)No BlueBlue, no , no corrosion of ironcorrosion of iron

Mg loses eMg loses e- - more more readily than iron.readily than iron.

Mg MgMg Mg2+2+ + 2e + 2e--

2)Some 2)Some BlueBlue, , corrosion of ironcorrosion of iron

Fe FeFe Fe2+2+ + 2e + 2e--

3)More intense 3)More intense BlueBlue, , corrosion of iron. corrosion of iron.

Fe loses eFe loses e- - more more readily than copper.readily than copper.

Fe FeFe Fe2+2+ + 2e + 2e--

QUESTION 1QUESTION 1 Attaching a metal that is higher in the ECS Attaching a metal that is higher in the ECS

Magnesium (Mg)Magnesium (Mg)

A) Protects iron from corrosionA) Protects iron from corrosion

B) Speeds up corrosionB) Speeds up corrosion

Attaching a metal that is lower in the Attaching a metal that is lower in the ECS Copper (Cu)ECS Copper (Cu)

A) Protects iron from corrosionA) Protects iron from corrosion

B) Speeds up corrosionB) Speeds up corrosion

QUESTION 2QUESTION 2

AttachingAttaching a metal that is higher in the a metal that is higher in the ECS (Mg)protects iron from corrosion, ECS (Mg)protects iron from corrosion, but attaching one that is lower down but attaching one that is lower down (Cu) speeds up its corrosion.(Cu) speeds up its corrosion.