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 is the methyle orange formula?, Methyl orange is a pH indicator often ...

Methyl orange is a pH indicator often used in titrations. It''s chemical formula  is C 14 H 14 N 3 NaO 3 S

Explain nitric oxide becomes brown when released in air, Give reasons for t...

Give reasons for the following: a. Molten aluminium bromide is poor conductor of electricity. b. Nitric oxide becomes brown when released in air. c. PCl

DSC., How to get Energy vs Temperature curve from DSC data

How to get Energy vs Temperature curve from DSC data

What is a safety management system, Question: (a) (i) What is a Safet...

Question: (a) (i) What is a Safety Management System? (ii) Outline the 5 basic components of a safety management system, as promoted by the International Labour Organi

Sources of aliphatic hydrocarbon, Sources of aliphatic hydrocarbon Mine...

Sources of aliphatic hydrocarbon Mineral or crude oil, petroleum is the dark colour oily liquid along with offensive odour found at several depths in many regions below the sur

Explain chemical equilibrium, Q. What do you know about Chemical Equilibriu...

Q. What do you know about Chemical Equilibrium Many chemical changes are reversible and will proceed towards an equilibrium instead of going to completion. The products react w

Homweoek help, Determine the rate constant from the concentration-time depe...

Determine the rate constant from the concentration-time dependence: Time (s) [Reactant](M) 0.0 0.0451 2.0 0.0421 5.0 0.0376 9.0 0.0316 15 0.0226 Use SI units, that is, seconds fo

Inorganic, what is diagonal relationship in periodic table

what is diagonal relationship in periodic table

Displacement of electron in covalent bond, a complete explnation about ind...

a complete explnation about inductive effect with example

Ionisation energy, Calculate energy of Rb per atom if light of wave length ...

Calculate energy of Rb per atom if light of wave length 5.4(10^-8)m produces electron with a speed of 2.450(10^6)

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