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?

Starch - polysaccharide or starch and cellulose, Starch and its derivative...

Starch and its derivatives Starch is a white amorphous substance along with no taste or smell. While heated to a temperature among 200-250 o C it changes into dextrin. At large

The number of electrons in the nucleus of c12 is, The number of electrons ...

The number of electrons in the nucleus of C 12   is (1) 6        (2) 12       (3)0      (4)3 Ans: 0

Matter, why the water is compound

why the water is compound

Concentration of electrons in the conduction band, Concentration of electro...

Concentration of electrons in the conduction band At equilibrium, there is no net current flowing across p-n junction. Concentration of electrons in the conduction band in cond

METAL COMPLEXES, Structure and IUPAC name of K3[Al(C2O4)3]

Structure and IUPAC name of K3[Al(C2O4)3]

Analytical chemistry, WHAT TYPE OF CHEMICAL REACTION IS INVOLVED IN POTENTI...

WHAT TYPE OF CHEMICAL REACTION IS INVOLVED IN POTENTIOMETRIC TITRATION

Properties of unsaturated halides (halo-alkene), Properties of Unsaturated ...

Properties of Unsaturated halides (Halo-alkene) Halo-alkene is a colourless gas at room temperature. The boiling point of it is -13°C. The halogen atom in vinyl chloride is not

PH value, how to calculate pH value?

how to calculate pH value?

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