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?

The de-broglie wavelength associated with material particle, The de-Broglie...

The de-Broglie wavelength associated with a material particle is: (1)  Directly proportional to its energy (2) Directly proportional to momentum (3) Inversely proportiona

Chemical kinetics, Distinguish between van''t Hoff Method and Oswald Isolat...

Distinguish between van''t Hoff Method and Oswald Isolation Method. In each case give an expression for the rate of reaction.

Hydroxides, Why do zinc hydroxide, aluminium hydroxide and lead (II) hydrox...

Why do zinc hydroxide, aluminium hydroxide and lead (II) hydroxide dissolve in excess aqueous sodium hydroxide?

Explain consumer testing, Consumer testing Consumer testing is the ne...

Consumer testing Consumer testing is the next crucial aspect in product development. Consumer testing can be done in three ways: 1.  In-house laboratory testing   2.  Ho

Calculate the amount of water, In a design of a tower, water is chilled fro...

In a design of a tower, water is chilled from T wa = 65°F to T wb = 45°F.  The inlet water is w a = 1000 lb/h.  Calculate the amount of water that evaporates and the mass flow of

What is sensory evaluation, Q. What is sensory evaluation? Foods have s...

Q. What is sensory evaluation? Foods have several characteristics that require evaluation by sensory methods. The various food attributes that are judged on the sensory scale a

Periodic Table, I think it''s funny how you guys say that you''re experts, ...

I think it''s funny how you guys say that you''re experts, but on the periodic table on the site you have the noble gases listed as inert elements. If whoever created that page act

Polymers, giving correct formulas give the reactantsand products in the for...

giving correct formulas give the reactantsand products in the formation of poly2 butane

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