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?

Mention the sampling stages of shelf life evaluation, Q. Mention the sampli...

Q. Mention the sampling stages of shelf life evaluation? The sampling stages of shelf life evaluation are: Experimental kitchen or pilot plant batch, full scale factory batch a

Inductive effect, Why inductive effect is compared with hydrogen?

Why inductive effect is compared with hydrogen?

What is tracers?, In the study of mechanisms of various chemical reactions,...

In the study of mechanisms of various chemical reactions, Deuterium and Tritium are used as tracers.

Why octahedral complexes of ni+2 must be outer orbitals?, The coordination ...

The coordination number of Ni in the complex is 4, the configuration of Ni +2 , at first sight, shows that the complex is formed by sp 3 hybridization  and it is paramagnetic an

Uses of benzene - hydrocarbon, Uses of Benzene - Hydrocarbon (1) In dry...

Uses of Benzene - Hydrocarbon (1) In dry cleaning (2) As a motor fuel when mixed with petrol. (3) As a solvent. (4) In the manufacture of gammexane (As insecticide).

Which the following sets of quantum numbers is not allowed, Which of the fo...

Which of the following sets of quantum numbers is not allowed : (1) n=1, l=0,m=0 s= +1/2                   (2) n=1, l=1,m=0 s= -1/2              (3) n=2, l=1,m=1 s= +1/2

Hydrogen., what are the chemical properties of protium, deuterium and triti...

what are the chemical properties of protium, deuterium and tritium.

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