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?

PH and DO, does lowered pH of water affect dissolved oxygen?

does lowered pH of water affect dissolved oxygen?

Sodium and chlorine reacts, When sodium and chlorine reacts then: (1) E...

When sodium and chlorine reacts then: (1) Energy is released and ionic bond is formed (2) Energy is released and a covalent bond is formed (3) Energy is absorbed and ioni

Lab prepation, How is ethane gas is preparec in the lab?

How is ethane gas is preparec in the lab?

Edta, #questionQ1. 0.28gm of CaCO3 was dissolved in HCl and the solution wa...

#questionQ1. 0.28gm of CaCO3 was dissolved in HCl and the solution was made to one litre with distilled water. 100 ml of the above solution required 28 ml of EDTA solution on titra

Determine stronger acidity of buffer, In order to additional explore the bi...

In order to additional explore the biochemistry of MSG action; we'd require having an aqueous buffer wherein to work. For this question, assume that you require making an 80 mM buf

Condensation reaction of carbonyl compounds, Condensation reaction of carbo...

Condensation reaction of carbonyl compounds Nucleophilic addition reaction of compounds comprising carbonyl group along with those compounds that have at least one acidic hydro

Determine chromium has the electronic configuration, Chromium has the elect...

Chromium has the electronic configuration 4s 1 3d 5 rather than4s 2 , 3d 4 because: (1) 4s and 3d  have the same energy (2) 4s  has a higher energy than 3d (3)4s 1   is

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