What is Corrosion

What is Corrosion?.

Corrosion can be defined as the destructive attack of a metal through interaction with its environment.

FORMS AND MECHANISMS OF CORROSION

DRIVING FORCE FOR CORROSION.

Most metals used in the construction of facilities are subject to corrosion. This is due to the high energy content of the elements in metallic form. In nature, most metals are found in chemical combination with other elements. These metallic ores are refined by man and formed into metals and alloys. As the energy content of the metals and alloys is higher than that of their ores, chemical re-combination of the metals to form ore like compounds is a natural process.

FUNDAMENTAL MECHANISM OF ATTACK.

Corrosion of metals takes place through the action of electrochemical cells. Although this single mechanism is responsible, the corrosion can take many forms. Through an understanding of the electrochemical cell and how it can act to cause the various forms of corrosion, the natural tendency of metals to corrode can be overcome and equipment that is resistant to failure by corrosion can be designed.

The Electrochemical Cell.

As in all chemical reactions, corrosion reactions occur through an exchange of electrons. In electrochemical reactions, the electrons are produced by a chemical reaction in one area, the anode, travel through a metallic path and are consumed through a different chemical reaction in another area, the cathode. In some cases, such as the common dry cell battery, electrochemical reactions can be used to supply useful amounts of electrical current. In marine corrosion, however, the most common result is the transformation of complex and expensive equipment to useless junk.