The Eurasia Proceedings of Science Technology Engineering and Mathematics

Abstract

Corrosion
can be defined as the deteoration of metals and alloys due to a interaction
with their environments. There are several types of corrosion such as general
corrosion , galvanic corrosion, pitting corrosion, intergranular corrosion,
atmospheric corrosion. Galvanic corrosion, also known as bimetallic corrosion,
is an electrochemical process which occurs when two different metals are
immersed in electrolytic solution due the difference of electrode potentials of
dissimilar metals. One of the metals is anode and other is cathode in the
couple. Metals and alloys have different electrode potentials. The less noble
metal is anode tends to corrode faster than cathode. The electrolyte acts as a
conductive noble metal is protected. Several factors affect galvanic corrosion
rate, such as potential difference between metals, cathode efficiency, surface
areas of the connected metals , electric resistance difference of the connected
metals and electrolyte. When a metal is in contact with a metal which is close in
galvanic series. For example, zinc aluminum couple shows 300mV potential in
sodium chloride solution whereas zinc copper couple indicates 700 mV. The greater
the potential difference, the greater the power to conduct galvanic corrosion.