Corrosion process and control (TKK-2289) 15/16 Semester genap Instructor: Rama Oktavian; Vivi Nurhadianty. Office Hr.: T , Th ; 13-15, F ; 13-15

Corrosion Definition (A)Corrosion is the surface wastage that occurs when metals are exposed to reactive environments. (B) Corrosion is the result of interaction between a metal and environments which results in its gradual destruction. (C) Corrosion is an aspect of the decay of materials by chemical or biological agents. (D) Corrosion is an extractive metallurgy in reverse. For instance, iron is made from hematite by heating with carbon. Iron corrodes and reverts to rust, thus completing its life cycle. The hematite and rust have the same composition (Fig. 1.1). (E) Corrosion is the deterioration of materials as a result of reaction with its environment (Fontana). (F) Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with the environment (Uhlig).

Corrosion Consequence of corrosion (A) Plant shutdowns (B) Loss of products, leaking containers, storage tanks, water and oil transportation lines and fuel tanks (C) Loss of efficiency (D) Contamination

Corrosion Corrosion may severely affect the following functions of metals, plant and equipment (A) Impermeability (B) Mechanical strength (C) Dimensional integrity (D) Physical properties (E) Contamination (F) Damage to equipment

Corrosion Why do we need to study corrosion? (A) Materials are precious resources of a country (B) Engineering knowledge is incompletewithout an understanding of corrosion (C) Several engineering disasters have been witnessed in recent years (D) Corrosion is a threat to the environment

Corrosion For corrosion to take place, the formation of a corrosion cell is essential -Anode -Cathode -Electrolyte - Metallic path.

Corrosion Anodic and cathodic reaction

Corrosion Anodic reaction characteristic Cathodic reaction characteristic Cathodic reactions are reduction reactions which occur at the cathode

Corrosion Mechanism of corrosion Details of reactions

Corrosion Corrosion as chemical reaction Corrosion in acid

Corrosion Corrosion as chemical reaction Corrosion in neutral and alkaline solution The corrosion of metals can also occur in fresh water, seawater, salt solutions, and alkaline or basic media. The most familiar corrosion of this type is the rusting of iron when exposed to a moist atmosphere

Corrosion Corrosion electrochemistry a piece of zinc immersed in hydrochloric acid solution is undergoing corrosion

Corrosion Corrosion electrochemistry

Corrosion Concept of free energy in electrochemical reaction The contribution made by one mole of any constituent, A, to the total free energy, G, of a mixture is G A, which may be represented by Gibbs–Helmholtz equation

Corrosion Concept of free energy in electrochemical reaction For reversible process At constant pressureAt constant temperature

Corrosion Concept of free energy in electrochemical reaction For chemical reaction for 1 mole of forward reaction At equilibrium

Corrosion Concept of free energy in electrochemical reaction Free energy as the driving force of chemical reaction

Corrosion Concept of free energy in electrochemical reaction Free energy as the driving force of chemical reaction

Corrosion Concept of free energy in electrochemical reaction Free energy as the driving force of chemical reaction

Corrosion Application of free energy to corrosion cell It is known that corrosion reactions produce electrical energy. The amount of work done by a cell is equal to the quantity of electrical energy which it generates under constant pressure, temperature and concentration of the reaction.

Corrosion Application of free energy to corrosion cell