I think I understand it as some metals are more prone to rust and wear then others? These are used as sacrificial pieces that dissolve(?) to prevent the item you’d like to preserve from wearing or rusting. Help me understand how for instance in a boat the Zink weight bolted to the propeller assembly slows the other metal parts from rusting, as in why do both the sacrificial puck of zinc and the propeller not rust away together when they’re both submerged in the ocean?
In: Chemistry
Sacrificial anodes aren’t for regular corrosion. Your steel hull will still rust and will still need to be scraped and painted to preserve it. Sacrificial anodes help with galvanic corrosion, which occurs when you have dissimilar metals in the presence of an electrolyte.
The more anodic metals will be eaten away, while the more cathodic metals will gain deposits on them. The idea for a sacrificial anode is that you intentionally add a more anodic material to protect what would otherwise be the anode in the system. For example, if your boat has an aluminum hull, steel screws will cause galvanic corrosion and cause the aluminum to be eaten away in spots. Adding zinc causes the zinc to be eaten away instead, and you simply replace it when you need to.
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