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?

Polarization in a dielectric on application electric field, Polarization in...

Polarization in a dielectric on application of electric field is Displacement/separation of opposite charge centres.

Calculating no. of atoms, Gold has a molar mass of 197g/mol. How many atoms...

Gold has a molar mass of 197g/mol. How many atoms are in the sample?Please give me procedure also. Ans) molecular wieght of gold is 197 g 1mole/g of molecule is occupies the

Oxidation and reduction, Which of the following reduces the activation ener...

Which of the following reduces the activation energy of a chemical reaction?

What do you mean by solids non-fat, Q. What do you mean by Solids Non-Fat? ...

Q. What do you mean by Solids Non-Fat? Solid non-fat is an important criterion of milk selection for further processing. Milk solids non-fat would include the nitrogenous subst

Chemical properties of aromatic nitro compounds, Chemical Properties of Aro...

Chemical Properties of Aromatic Nitro Compounds Resonance in nitrobenzene pass on a partial double bond character to the bond among carbon of benzene nucleus and nitrogen of th

LATIMER, WHAT IS THE FEROST DIAGRAM

WHAT IS THE FEROST DIAGRAM

Chemical properties proteins - hydrolysis, Chemical Properties Proteins - H...

Chemical Properties Proteins - Hydrolysis Hydrolysis : The very simple proteins are hydrolysed by acids, alkalies or enzymes to generate amino acids. Subsequent steps are inclu

Physical properties of cycloalkane, Physical properties of Cycloalkane ...

Physical properties of Cycloalkane  (i) In Cycloalkane First two members are gases, next three members are liquids and higher ones are solids. (ii) Cycloalkane is not solubl

Copper, stuck on a chemistry assignment i need a way to include the elctron...

stuck on a chemistry assignment i need a way to include the elctron configuration and chemical properties of copper into a oral that is also a sales pitch.

Formic acid or methanoic acid or hcooh, Formic Acid or Methanoic acid (HCOO...

Formic Acid or Methanoic acid (HCOOH) Formic acid is the very first member of monocarboxylic acids series. It takes place in the sting of bees, wasps, red ants, stinging nettle

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