Which metal object may be least affected by galvanic corrosion when submerged in seawater?

The stainless steel propeller shaft is the metal object that may be least affected by galvanic corrosion when submerged in seawater. This is primarily due to the properties of stainless steel, which contains chromium. The presence of chromium allows stainless steel to form a passive oxide layer on its surface, which helps to protect it from corrosion, including galvanic corrosion.

Galvanic corrosion occurs when two dissimilar metals are in electrical contact in a corrosive environment, such as seawater. Different metals have different electrochemical potentials, and when they are connected, the more noble metal tends to stay less corroded compared to the less noble one. Stainless steel is more noble than metals like aluminum or iron, meaning it will corrode at a much slower rate when in contact with these metals, especially in a marine environment.

In contrast, copper, aluminum, and iron are all less resistant to galvanic corrosion when exposed to seawater. Copper can corrode significantly when in contact with aluminum, for example, and iron is prone to rust which leads to rapid deterioration. Thus, the intrinsic properties of stainless steel make it the best option to resist galvanic corrosion in such environments.