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?

What are the functional groups in aspartame?, Carboxylic group,amino group,...

Carboxylic group,amino group,ester group,amide group group are key functional groups in aspartame although phenol is present it is not a functional group.

Atomic structure, how ti find numbeer of neutrons in dipositive zinc ion wi...

how ti find numbeer of neutrons in dipositive zinc ion with mass number 70?

Full Balanced Equations, #question.What is the balanced equation for the re...

#question.What is the balanced equation for the reaction of aluminium nitrate solution and sodium carbonate solution; where aluminium hydroxide is formed.

Benzaldehyde, Preparation of benzaldehyde by etard''s reaction

Preparation of benzaldehyde by etard''s reaction

Chemical Equilibrium, why is the reaction mixture does not have 50% reactan...

why is the reaction mixture does not have 50% reactants and 50% products?

Solid state, how many solid state are there?

how many solid state are there?

Explain resonance effects, Explain Resonance effects Resonance effects:...

Explain Resonance effects Resonance effects:  The application of the resonance effect for predicting the relative rates of acid-catalyzed ester and amide hydrolyses is exactly

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