Overview
Zinc anode is the protection you need for your boat's metallic parts. Referred to as sacrificial anodes, these anodes are placed over and connected to the metallic parts of your boat that need protection from electrolysis-caused corrosion. Corrosion occurs from electrolysis; the wearing off of the metal that is caused by the current-equalizing effect on the different metals that are dipped in water.
Why Zinc?
Anodes can be made from magnesium, aluminum, zinc, or alloys (combination of metals). The preference for zinc anodes stems from the fact that zinc has a higher voltage conduction than these other metals. As such, whenever zinc is connected to other voltage conductors (that make the different parts of your boat), current flows more through zinc than it does the other parts; limiting electrolysis to zinc alone.
When should you change your zinc anode?
If your boat's voltage input and output are healthy (not faulty), your zinc anode should last more than a year. However, if you find high quantities of zinc residue on your boat's rudder, shaft or any of the parts covered with zinc, you should replace the anodes. You might also need to get a certified-technician to inspect your boat's voltage input and output to ascertain the source of the excessive/ faulty voltage.
Additional precaution
While the wiring in your boat may be perfect, shore power supplies may not always be properly done. You should, therefore, install a shore power ground lead or a copper 'fish' in addition to the zinc anodes. Faulty power supplies disrupt a healthy current flow through your boat's parts and this may cause your boat's zinc anode to corrode faster than normal. If you fail to check your zinc anode regularly, then the voltage overload may corrode it and start corroding your boat's parts without your knowledge. The shore power ground lead gives the excessive or misplaced current an exit.
Conclusion
The metallic parts of your boat need to be insulated with zinc anode to prevent their corrosion. Zinc, being a high voltage conductor, ensures that the current flowing through your boat and the water exits from the zinc anode. The anodes must be connected to the parts that need protection and to the boat's negative bonding system.
Deep Blue Yacht Supply carries the entire line of Zimar Zinc Anodes, and can ship worldwide. Zimar Zincs are often referred to as the absolute best zincs in the marketplace.