🔍 Key Concepts

• Galvanic series of metals in seawater and which metals are more active (anodic) vs more noble (cathodic) • Purpose of a sacrificial anode in protecting steel hulls, tanks, and underwater fittings • Common materials used on ships and small boats for cathodic protection (think about zincs on shafts, rudders, and hulls)

💭 Think About

• Which of these metals is commonly seen bolted to hulls, shafts, or rudders specifically labeled as "anodes" on vessels? • In corrosion protection, do we want the sacrificial metal to be more reactive (less noble) or less reactive (more noble) than the metal we are protecting? Which option matches that? • Think about cost and practicality: which listed metal is cheap, soft, and easy to replace, and which are too valuable or not suitably reactive for use as a sacrificial anode?

✅ Before You Answer

• Verify which choice is commonly referred to as a "hull zinc" or shaft anode on boats and ships • Eliminate metals that are too noble (resistant to corrosion) to act as sacrificial anodes effectively • Confirm that the selected metal is widely used in cathodic protection systems for marine structures and ship hulls