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ABOUT CORROSION

CORROSION




It is defined as the chemical or electrochemical attack of metals by the environment.

the effects of corrosion by these factors;


  • humidity
  • temperature
  • purity of  metal
  • the physical state of metal
  • nature of ions present in it
  • PH
  • position in electrochemical series
  • relative areas of anode and cathode

electrochemical theory of corrosion;


this theory depends on its electrode potential of metal(anode).if a high electrode metal comes in contact with the low electrode(cathode) potential metal causes the galvanic cell setup.

note: the large corrosion occurs at anodic metal.

the galvanic cells are three types:


composition cell;

in this, both the zinc and copper electrodes are dipped in the same electrolysis solution. 
here the zinc is act as anode and the copper is act as like cathode.the electrons are transferred from anode to cathode.here the anode gets corroded.

stress cell;

These types of cells formed by the drawing, rolling, welding, heat treatment of metals.
stressed areas at the metal act as like an anode causes corrosion.

concentration cell;

this type of cells formed the differential oxygen concentration.poor oxygenated parts act like anodes and causes the corrosion.

RUSTING OF IRON:


  • (Fe2O3xH2O)
  • corrosion of iron is called rusting.

prevention methods for avoiding:

  • using metal high purity
  • alloying
  • protective coating by the metallic or non-metallic or organic.

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THERMODYNAMIC LAWS

 HELLO ALL, TODAY I WANT TO EXPLAIN ABOUT THE THERMODYNAMIC LAWS thermodynamic laws are : 1. first law: it states that energy neither be created nor be destroyed, it always changes one form to another form. 2. second law: it states that energy can change the position of any object but the state of energy is potentially reduced comparing to the initial state. 3. third law: it states that the thermal energy per unit temperature of a system approaches a constant value as the temperature absolute zero. zeroth law: if two systems are in thermal equilibrium with the third system then these three are also in thermal equilibrium.
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THE EYE OF THE HUMAN

the human eye is the sense organ in the body to see and identify the objects. the cornea is a layer of the eye that protects eye from the dust and it acts as a protective membrane. behind the cornea, a humorous liquid is filled in a space. the iris contains a pupil in it, iris allows the light to pupil.iris is a muscular diaphragm. the pupil is a hole.it catches the light and does not reflect back.it is in black color. the lens is the backward covered portion to form the image from the retina. NOTE 1: the distance between the lens and retina is about 2.5 cm. due to the deficiency of vitamin A in our body, these symptoms may cause to eye:  night blindness, cornea failure. the retina contains the 125 million receptors called rods and cones which receives the light signal data from the eye and sends it to the brain through 1 million optic nerves.   NOTE 2: the lenses are; concave,convex,bi concave,bi convex,plano concave,plano convex, concavo-convex. HUMAN EYE SIGHTS: there are ...
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