Question

what is corrosion ?

Answer 1

Whent the surface of a metal is attacked by air, moisture or any other substances around it, the metal is said to corrode and the phenomenon is known a corrosion . It is also called weeping of the metal..

In such a process mostly metal oxides are formed, but if metals contain impurities like carbon and sulphur they may form sulphides and carbonates as well..

example..
1) aluminum and magnesium form white colour oxide on exposure to atmosphere
2) Iron forms hydrated oxide which is brown in colour known as rust..
3) Silver gets tarnished when exposed to atmosphere which contains pollutant H2S and forms black coating of Ag2S

Answer 2

Hey there!

Answer:


When metals are exposed to atmospheric conditions, they react with air or water in the environment to form undesirable compounds ( usually oxides) is called $\textbf{corrosion}$. 


Almost all $\textbf{metals except }$ the least active metals such as $\textbf{gold, platinum }$ are attacked by environment i.e, undergo corrosion. 


$\textbf{For Example}$ : Silver tarnishes, copper develop a green coating, lead or stainless steel lose their lusture due to corrosion. Corrosion causes enormous damage to buildings, $\textbf{bridges, ships}$ and many other articles made of iron.


$\large{Thus\: corrosion}$ , Is a process of deterioration of a metal as a result of its reaction with air or water surrounding it.


$\textbf{\underline{Factors\: which\: affect corrosion}}$ : 


a) $\textbf{Presence of Co2 in water}$ , increases the rusting of the iron. Water containing $\Co_{2}$acts as a electrolyte and increases the flow of electrons from one place to another place.


b) $\textbf{Presence of impurities in metals}$ : The impurities help in setting up voltaic cell, which increases the speed of the corrosion.


c) $\textbf{Presence of electrolytes}$, In water also increases the rate of corrosion, For example, corrosion of iron in sea water takes place to larger extent than in distilled water.


d) $\textbf{Position of metal in e.m.f series}$: The reactivity of metal depends upon its position in the electrochemical series. More the reactivity of metal, the more will be the possibility of the metal getting corroded.



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