What is galvanic corrosion, and why do boats often have sacrificial anodes (zincs) fitted to underwater metal fittings?

A. Galvanic corrosion only occurs above the waterline, so anodes are purely decorative

B. When two dissimilar metals are both immersed in an electrolyte like seawater and electrically connected, a small current flows and the more reactive metal corrodes preferentially — a sacrificial anode is deliberately made of an even more reactive metal so it corrodes first, protecting the more valuable fittings (propeller, shaft, skin fittings) instead

C. Galvanic corrosion is entirely prevented simply by using stainless steel fittings throughout

D. Anodes are fitted only to prevent osmosis in GRP hulls

A. Nothing — a test lift can proceed immediately after repairs

B. Testing should wait until cargo operations begin

C. The area within the grab's swing radius should be cleared of personnel before the lift

D. Only the crane operator needs to be aware the lift is happening

A. Who must remain clear of the exclusion zone while the lift takes place

B. The lunch schedule for the deck team

C. Only the weather forecast for the next watch

D. The cargo manifest for the next port