Unit 3 corrosion & batteries

Unit 3 Corrosion And Batteries Sept. /06 MA/chem/RCET

[object Object],Sept. /06 MA/chem/RCET

CORROSION ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Sept. /06 MA/chem/RCET metal Metal oxide Corrosion ,oxidation Metallurgy ,reduction Higher energy Lower energy

Example ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Classification Sept. /06 MA/chem/RCET dry wet other oxidation By gases liquid Evolution of H 2 Absorption of O 2

Dry / chemical corrosion ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Oxidation corrosion ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Over all reaction ,[object Object],Sept. /06 MA/chem/RCET Metal ion Oxide ion Metal oxide

Oxidation corrosion Sept. /06 MA/chem/RCET M M n+ + ne - Reaction at metal – metal oxide interface Atmospheric oxygen metal

Chemical reaction ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

TYPES ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

1 .stable ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

2. Unstable Sept. /06 MA/chem/RCET metal metal metal Exposed surface O 2 ,air Unstable metal oxide Film formed decomposed + O 2

3. Volatile Sept. /06 MA/chem/RCET metal metal metal Exposed surface O 2 ,air volatile metal oxide Film formed decomposed + O 2

4. Porous Sept. /06 MA/chem/RCET metal metal Exposed surface O 2 ,air porous metal oxide Film formed decomposed + O 2 Further attack through cracks ,pores

Corrosion by other gases ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Liquid metal corrosion ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Wet corrosion ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Cathodic reaction ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Evolution of hydrogen ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Chemical reaction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Evolution of hydrogen Sept. /06 MA/chem/RCET M M n+ + 2e - Acidic solution ,electrolyte Small ,cathodic area Large anodic area

Absorption of oxygen ,[object Object],[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Absorption of oxygen Sept. /06 MA/chem/RCET Aqueous neutral solution rust Large cathodic area Small anodic area

Anodic reaction ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Cathodic reaction ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

( i ) ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

( ii ) ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

GALVANIC (OR BIMETALLIC) CORROSION ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Galvanic / Bimetallic Sept. /06 MA/chem/RCET Zn Cu Electronic current Cathode ,protected Anode , attacked electrolyte

Explanation ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Mechanism ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Examples ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

CONCENTRATION CELL CORROSION ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Concentration cell corrosion Sept. /06 MA/chem/RCET Water line corrosion Zn rod Corroding anode NaCl solution More oxygenated part Less oxygenated part

[object Object],[object Object],Sept. /06 MA/chem/RCET

[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

Chemical reaction ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

PASSIVITY ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Passivity falling order ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

8. UNDERGROUND OR SOIL ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

(a) ,[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

(b) ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

corrosion depends ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

9. PITTING CORROSION ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Breakdown of the protective film ,[object Object],[object Object],[object Object],[object Object],Sept. /06 MA/chem/RCET

INTERGRANULAR CORROSION ,[object Object],[object Object],Sept. /06 MA/chem/RCET

Unit 3 corrosion & batteries

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