Question 3-3A3

Galvanic corrosion occurs when two dissimilar metals are in electrical contact and submerged in an electrolyte, such as seawater. The more "active" or anodic metal will corrode, sacrificing itself to protect the more "noble" or cathodic metal. Stainless steel, particularly marine grades (like 316), is relatively noble (cathodic) in seawater compared to aluminum, bronze, and lead. Therefore, a stainless steel propeller shaft is the *least* likely to corrode when coupled with these other common marine metals, as it tends to act as the cathode in a galvanic cell. Conversely, an aluminum outdrive is very anodic and highly susceptible to rapid corrosion in seawater. Bronze through-hulls and exposed lead keels are also significantly more anodic than stainless steel and would corrode more readily if coupled with a more noble metal or when acting as the anode. Understanding these material properties is vital for preventing equipment failure in marine radio installations.