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 an emulsifier, Q. What is an Emulsifier? An emulsifier is a co...

Q. What is an Emulsifier? An emulsifier is a compound that contains both polar and nonpolar groups and thus is drawn to the interface between the two phases of an emulsion to

Show the chemical properties of group 13, Q. Show the Chemical Properties o...

Q. Show the Chemical Properties of Group 13? Elements of Group 13 are comparatively less reactive than the alkali and alkaline earth metals of Groups 1 and 2 However, the +acti

The wall thickness can be minimized by insulation layer, The wall thickness...

The wall thickness can be minimized by insulation layer The wall thickness can be minimized by insulation layers. A typical wall having of a brick layer that has a thickness of

Define heat and temperature, Q. What is basic diffrence between heat and te...

Q. What is basic diffrence between heat and temperature? Ans. Heat is energy which flows from hot objects to cooler ones.  It flows because of the temperature difference betw

Uses of aromatic nitro compounds, Uses of Aromatic Nitro Compounds (a) ...

Uses of Aromatic Nitro Compounds (a) Aromatic Nitro Compounds are used on account of their high polarity, aromatic nitro compounds are used as solvents. (b) Nitro compounds

Anti-malarials - drugs and medicines, Anti-Malarials: Malaria is very ...

Anti-Malarials: Malaria is very wide spread infectious disease, initiate by sporozoa of genus plasmodium. It is characterized clinically through anaemia, periodic fever, enlar

Electrolysis of water, Electrolysis of Water without Indicator • Assembl...

Electrolysis of Water without Indicator • Assemble the power supply for electrolysis. Attach alligator clips to the separate poles of the battery. Make sure that the wires from

P block, why ionisation energy of aluminium is greater then Ga?

why ionisation energy of aluminium is greater then Ga?

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