🔍 Key Concepts

• seawater corrosion mechanisms on steel shafts • difference between temporary coatings (like grease or paint) and permanent physical protection • how abrasion and rotation of a propeller shaft affect any protective material

💭 Think About

• For each option, ask yourself: Will this survive long-term on a rotating shaft that is constantly in seawater and subject to sand, silt, and marine growth? • Consider which methods are normally used for underwater metal protection on moving parts versus methods used on hull surfaces. • Think about whether relying on an existing corrosion layer is actually considered protection in marine engineering.

✅ Before You Answer

• Eliminate any option that would quickly wash off or wear away on a spinning shaft. • Focus on methods that provide a durable, physical barrier between seawater and the metal of the shaft. • Ask whether the method described is something a classification society or shipyard would realistically approve for submerged, rotating machinery.