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7 March 2026 · 4 min · 1K views
Diver inspects propeller zinc anode underwater
What this video covers
Jan Attenstedt and Nigel Calder analyze the corrosion rates of sacrificial anodes on a custom sailboat equipped with a copper bonding system.▶ 0:12 The vessel features isolated anodes on the propeller, propeller shaft, and bow thruster, but lacks a hull-mounted anode.▶ 0:32 The owner reports replacing the propeller zinc mid-to-late season, while other anodes retain over 50% of their material.▶ 0:41 Calder identifies the internal copper bonding strap as likely part of a lightning protection system rather than a galvanic corrosion protection system.▶ 1:47 He notes that isolated underwater components naturally exhibit varying rates of anode consumption.▶ 1:40 While replacing a propeller zinc annually is common, rapid consumption suggests high variability in interaction between the bronze propeller and the anode.▶ 2:58 Calder recommends replacing zinc anodes with aluminum, which typically offers a longer service life.▶ 3:32 He warns that mixing anode materials within a common bonding system is prohibited, though isolated components can use different metals.▶ 3:30
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