Galvanic Corrosion

Abstract

Corrosioncan be defined as the deteoration of metals and alloys due to a interactionwith their environments. There are several types of corrosion such as generalcorrosion , 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 areimmersed in electrolytic solution due the difference of electrode potentials ofdissimilar metals. One of the metals is anode and other is cathode in thecouple. Metals and alloys have different electrode potentials. The less noblemetal is anode tends to corrode faster than cathode. The electrolyte acts as aconductive noble metal is protected. Several factors affect galvanic corrosionrate, such as potential difference between metals, cathode efficiency, surfaceareas of the connected metals , electric resistance difference of the connectedmetals and electrolyte. When a metal is in contact with a metal which is close ingalvanic series. For example, zinc aluminum couple shows 300mV potential insodium chloride solution whereas zinc copper couple indicates 700 mV. The greaterthe potential difference, the greater the power to conduct galvanic corrosion.