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?

Determine the concentration of hydroxide ion in this buffer, In lab, buffer...

In lab, buffers solution based onto a 0.1 M solution of sodium phosphate at pH7.0.  Within this system, there are three of pK A s like:  12.7, 7.21 and 2.12. Determine the conce

Degree of superheat, How to know degree of superheat from psychometric char...

How to know degree of superheat from psychometric chart?

Show diffrent type of ligands, Q. Show diffrent type of Ligands? Ligand...

Q. Show diffrent type of Ligands? Ligands which contain one donor atom are called monodentate the donor atom may contain One or  more than one lone pairs of electrons. The l

Inorganic chemistry, dipole moment of para.nitro aniline is 6.10 D.why

dipole moment of para.nitro aniline is 6.10 D.why

Crystal by anion and cation, Bond formed in crystal by anion and cation is:...

Bond formed in crystal by anion and cation is: (1) Ionic    (2) Metallic  (3) Covalent    (4) Dipole Ans:  Ionic

Berzilius hypothesis, explain Berzelius hypothesis and contradiction of dal...

explain Berzelius hypothesis and contradiction of daltons hypothesis with an example

P-orbitals of an atom in presence of magnetic, p-orbitals of an atom in pre...

p-orbitals of an atom in presence of magnetic field are: (1)  Two fold degenerate (2) Non degenerate (3) Three fold degenerate (4) None of these Ans: Non degenerate

Types of interferences - atomic absorption spectrophotometry, Types of inte...

Types of interferences - Atomic absorption spectrophotometry: Three types of interferences viz., chemical, spectral and physical interferences are encountered in AAS. These re

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