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?

Crude and dietary fibre, Q. Crude and Dietary Fibre? Crude fibre is the...

Q. Crude and Dietary Fibre? Crude fibre is the organic residue which remains after the food sample has been treated with boiling dilute sulphuric acid, boiling dilute sodiu

How does vulcanization change the natural rubber, a. How does vulcanization...

a. How does vulcanization change the character of natural rubber? b. Why are the numbers 66 and 6 put in the names of nylon-66 and nylon-6?

Burgers vector in screw dislocation, Burgers vector in screw dislocation ...

Burgers vector in screw dislocation The  Burgers vector, often signified by  b, is a vector that shows the magnitude and direction of the lattice distortion of dislocation in a

Organic compounds., methods of purification of organic compounds with diagr...

methods of purification of organic compounds with diagrams ..

Experimental evidence the existence of the atomic nucleus, Experimental evi...

Experimental evidence for the existence of the atomic nucleus comes from: (1) Millikan's oil drop experiment (2) Atomic emission spectroscopy (3) The magnetic bending of

Explain reaction for benzyl chloride to benzyl alcohol, How are the followi...

How are the following conversions carried out? (i)  Benzyl chloride to benzyl alcohol, (ii)  Methyl magnesium bromide to 2- methlpropan -2-ol,

Separation of mixtures, name the easiest method of obtaining diesel from a ...

name the easiest method of obtaining diesel from a mixture of petrol and diesel.

Chemicals in food, Chemicals in food Several chemicals are added to foo...

Chemicals in food Several chemicals are added to food for their preservation and improving their appeal. These involve flavorings, antioxidants, fortifiers, sweeteners, dyes, e

Describe properties of potassium permanganate., Potassium permanganate is p...

Potassium permanganate is prepared from pyrolusite  (MnO 2 ) . Pyrolusite is fused with KOH in the presence of atmospheric oxygen or an oxidising agent like potassium nitrate or po

F block, Write the electron configuration for Tl why do we use F block and ...

Write the electron configuration for Tl why do we use F block and how do i count the subshells in that case?

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