Sailing Zephyr IVvideo
This Bronze Propeller Dissolved in Saltwater - Here's Why
January 29, 2024 · 8 min · 3K views
What this video covers
Galvanic corrosion occurs when dissimilar metals, such as a stainless steel propeller shaft and a bronze propeller, are immersed in an electrolyte like seawater.0:50 This electrochemical process creates a small voltage, causing the tin in the bronze alloy to leach out and leaving behind soft, porous copper that erodes under mechanical stress.2:54 To prevent this, boat owners must install sacrificial anodes made of a less noble metal, typically zinc, which corrodes preferentially to protect the bronze components.3:38 On Zephyr IV, the owner ensures electrical continuity by bonding the anode bolts to the engine, cooling seacocks, and hull fittings using internal wiring.4:41 Anodes require a clean electrical connection to function; if an anode shows no signs of erosion after a year, it is likely isolated from the protected parts.5:38 Beyond hull-mounted anodes, shaft-mounted anodes and hub-mounted anodes for bow thrusters provide localized protection.6:50 Regular inspection and annual replacement of eroded anodes prevent structural failure of underwater bronze fittings.5:09
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