Galvanic corrosion:

Galvanic corrosion occurs while two dissimilar metals along with different potentials are placed in electrical contact in an electrolyte. It might also take place along with one metal within heterogeneities (dissimilarities) (for instance, impurity inclusions, grains of various sizes, variations in composition of grains, or variations in mechanical stress). The difference in electrical potential exists among the different metals and serves as the driving force for electrical current flow by the corrodant or electrolyte.  That current result within corrosion of one of the metal.  The larger the potential difference, the greater the possibility of galvanic corrosion. A Galvanic corrosion just causes deterioration of one of the metals. A less resistant, more active one becomes the anodic (negative) corrosion site. The stronger, nobler one is cathodic (positive) and protected.  The two metals would be uniformly attacked through the corrosive medium if there were no electrical contact.  This would then be known as common corrosion.

For any particular medium, a list could be made arranging metals sequentially from most active, to passive, or least noble, or most noble. A galvanic series for sea water is elaborate in the Chemistry Fundamentals Handbook.

Galvanic corrosion is of particular concern in design and material selection. Material selection is important since various metals come into contact along with every other and might form galvanic cells. A Design is significant to minimize differing flow conditions and resultant areas of corrosion buildup. The Loose corrosion products are important since they could be transported to the reactor irradiated and core.

In a few instances, galvanic corrosion could be helpful in the plant. For instance, the zinc will become the anode, and it will corrode if pieces of zinc are attached to the bottom of a steel water tank. The steel in the tank becomes the cathode, and it will not be affected through the corrosion. This method is known as cathodic protection. A metal to be protected is forced to become a cathode and it will corrode at a much slower rate than the other metal that is used as a sacrificial anode.