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 basic Corrosion electrochemistry Pourbaix diagram Potential–pH diagrams - represent the stability of a metal as a function of potential and pH - analogues to phase equilibrium diagrams. These diagrams are constructed from calculations based on Nernst equations and solubility data for metal and its species.

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Characterization of Pourbaix diagram

Corrosion basic Corrosion electrochemistry Regions in Pourbaix diagram

Corrosion basic Corrosion electrochemistry Regions in Pourbaix diagram Immunity Region - indicates that corrosion cannot occur in this region Corrosion Region -As iron is transformed to soluble species, it is expected that iron would corrode Region of Passivation - Metals like aluminum and steel are known to resist corrosion because of development of oxide films in the air

Corrosion basic Corrosion electrochemistry Benefits of Pourbaix diagram The information in the diagrams can be beneficially used to control corrosion of pure metals in the aqueous environment. By altering the pH and potential to the regions of immunity and passivation, corrosion can be controlled

Corrosion kinetics Faraday’s law of electrolysis The First Law The mass of primary products formed at an electrode by electrolysis is directly proportional to the quantity of electricity passed

Corrosion kinetics Faraday’s law of electrolysis The Second Law The masses of different primary products formed by equal amounts of electricity are proportional to the ratio of molar mass to the number of electrons involved with a particular reaction

Corrosion kinetics Faraday’s law of electrolysis Combining the first and second law, Where F is Faraday’s constant, the value is 96,485 coulombs per gram equivalent or 96,485 coulombs per mole of electron.

Corrosion kinetics Application Faraday’s law in determination of corrosion rate Corrosion rate has dimensions of mass × reciprocal of time: In terms of loss of weight of a metal with time Dividing equation (3.5) by the exposed area of the metal in the alloy

Corrosion kinetics Application Faraday’s law in determination of corrosion rate is current density (i) Practical unit for corrosion rate is millimeter per year (mmy −1 ) and mils per year (mpy)

Corrosion kinetics Application Faraday’s law in determination of corrosion rate Example

Corrosion kinetics Application Faraday’s law in determination of corrosion rate Example

Corrosion kinetics Application Faraday’s law in determination of corrosion rate Example

Corrosion kinetics Application Faraday’s law in determination of corrosion rate Example