Prevention of Galvanic Corrosion:

A method known as cathodic protection, discussed previously within this module, is frequently used to retard or eliminate galvanic corrosion.  One of various ways of accomplishing this is to attach a third metal to the metals to be protected.  This metal must have an oxidation potential even greater than in which of the metal to be protected.  The most active metal then tends to corrode within place of the protected metal. The metal which corrodes to protect another metal is known as a sacrificial anode. This technique is applied within the original design of structural materials. Zinc is a general sacrificial anode and is frequent used in cooling water systems which holds seawater.

Galvanic corrosion could also be limited through:  1) using just metals which are close on the activity series (discussed in the chapter on Corrosion Theory), 2) electrical insulation of dissimilar metals, and 3) by using poorly-conducting electrolytes (extremely pure water).

The associative surface areas of the two metals are also significant.  A much larger surface area of the non-active metal, compared to the active metal that will accelerate the attack.  It has been determined in which the associative surface area is the determining factor within the corrosion rates.

The needed electrical current for galvanic corrosion will be stopped if the unlike metals are:

1 separated through a non-conducting junction,

2 separated from a conductive environment, and

3 located in a poorly conducting electrolyte (pure water).