What is rusting electrochemical theory?, Chemistry

Assignment Help:

According to this theory, the impure iron surface behaves like a small electrochemical cell presence of water containing dissolved oxygen or carbon dioxide. Such a cell is also called corrosion cell or corrosion couple. In these miniature corrosion cells, pure iron acts as anode and impure surfaces acts as cathode. Moisture dissolved oxygen or carbon dioxide in it comprises electrolytic solution.


At anode, oxidization of Fe atoms takes place. Thus, Fe atoms pass into solution as Fe2+ ions leaving behind electrons in the metal which are pushed into cathodic area.
                                              
Fe  2370_halides.png  Fe+2 + 2e-;  604_Rusting theory.png = - 0.44 V        (i)


At cathode, the electrons are picked up by the H+ ions which are produced either from H2O or from H2CO3 (formed by dissolution of CO2in moisture).
                                 
CO2 + H2O  2370_halides.png  H+ + HCO3-
                           
2H+(aq) + 2e-  2370_halides.png  2H


The H atoms, thus, formed, reduce the dissolved oxygen as
                                 
2H + ½ O2  2370_halides.png  H2O

The net reduction process at the cathodic area is
                        
2H + ½ O2 + 2e-  2370_halides.png  H2O; 1581_Rusting theory1.png = 1.23 V                      (ii)


The net reaction of the corrosion cell can be obtained by adding equations (i) and (ii)
                                     
F2 + 2H+  2370_halides.png   ½O2 
                               
2 Fe2+ + H2O;  = 1.67 V


The ferrous ions so formed move through water and come at the surface of iron object where these are further oxidized to ferric state by atmospheric oxygen and constitute rust which is hydrated iron (III) oxide.
                  
2Fe2+ + ½ O2 + 2H2O  2370_halides.png  Fe2O3 + 4H+
                                 
Fe2+ + xH2O  2370_halides.png  Fe2O3xH2O (rust)

 

 

 

 

 


Related Discussions:- What is rusting electrochemical theory?

Conformation energy profile for butane c2-c3 bond rotation, Conformation en...

Conformation energy profile for butane Conformation energy profile for butane C2-C3 bond rotation

Freezing Point Lowering, The freezing point of ethylene glycol is -3.2 degr...

The freezing point of ethylene glycol is -3.2 degree-Celcius. How many grams of ethylene glycol is required in 150 L of water to achieve such temperature?

Balancing equations, What methods can I use to understand balancing equatio...

What methods can I use to understand balancing equations?

Line spectrum, Line Spectru- A emission spectrum that contains very sharp p...

Line Spectru- A emission spectrum that contains very sharp peaks (Prism Like Structure) , corresponding to transitions between states in free atoms.For example, the line spectrum o

Prefixes, why we consider methyl using prefixes?

why we consider methyl using prefixes?

Thermoplastic and thermosetting plastic resins, Q.  Differentiate the ther...

Q.  Differentiate the thermoplastic and thermo sets.                                   OR Write note on thermoplastic and thermosetting plastic resins. Ans.  T

Homologous, what do you mean by homologous series .

what do you mean by homologous series .

The number of electrons in cl- ion is, The number of electrons in c l -  ...

The number of electrons in c l -  ion is: (1) 19      (2) 20      (3) 18     (4) 35 Ans: 18

Purification and characterisation of acetone , What is this characterisatio...

What is this characterisation all about?and how do you do it using DNPH?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd