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INTRODUCTION


Metals are one of the main materials in construction. They play different roles in different building components. Some are structural and some are functional. Despite their functions, they all have a tendency to corrode when contact with oxidising agents ,such as water and oxygen. Corrosion not only can deteriorate the physical properties (e.g. appearance) of the relative metals, but also the chemical properties (e.g. strength). Corrosion can be classified as the followings:

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Corrosion

  Direct Chemical Corrosion

Electrochemical Corrosion

Destructive Corrosion Protective Corrosion

Crevice Corrosion

Galvanic Corrosion

           

In this thesis, the galvanic corrosion is mainly mentioned.

Galvanic corrosion is a corrosion usually resulting from a complex electrochemical action. Where two dissimilar metals which are electrically connected as well as immersed in an electrolyte, as a conducting liquid, for example, water, a short circuited galvanic cell is formed. In two metals, the more reactive one (tends to have reaction by giving up its electrons) will become the anode, change into the form of cations (positive ions) and then be removed. The less reactive metal at cathode will be so protected.

The protection of metals is very important no matter what kind of corrosion occurs.

                                                                       

                                                                         BY

                                                                               9600 2037 WONG WAI YIP, VICTOR

9600 4983 YEONG CHI YAN, MICHAEL


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