| hear talk about the docks regarding zincs, but what | | | | Yacht Props and Rudders |
| do they really do? How do they work? | | | | Propellers and shafts are normally protected by a zinc |
| Any time you have two different metals that are | | | | collar bolted together around the shaft. It is |
| physically or electrically connected and immersed in | | | | necessary to make sure the shaft is clean and |
| seawater, they produce electrical current. Some DC | | | | polished before clamping the collar to it. |
| current flows between the two metals which can | | | | Metal rudders and struts are protected with zinc |
| corrode metals such as props, shafts, thru hulls and | | | | disks bolted directly to the metal. Be sure bottom |
| sea strainers in the engine room. | | | | paint does not cover them. |
| The way we stop galvanic corrosion is to add a piece | | | | Yacht Hull Plates |
| of metal called a sacrificial anode, and most often it is | | | | Hull plates are used to bond the boat metals inside |
| zinc. In fact, most of us refer to sacrificial anodes | | | | the boat not directly exposed to salt water. |
| simply as zincs. Using zinc anodes on your boat is | | | | Bonding is the connecting together of zinc plates |
| very important. The anode will be used to corrode | | | | bolted to the hull to other metals. All the underwater |
| away before your boat equipment does. | | | | gear and the metal inside the engine room is |
| On the Galvanic Scale, Zinc is number 4, 1 being the | | | | connected to these plates. Be sure you check the |
| most sacrificial to seawater, Aluminum is 12, Steel is | | | | bonding between thru-hulls and other metal gear by |
| 30, Brass is 51, 316 Stainless is 76 and pure Gold is 91. | | | | the use of a multi-meter set on the ohm settings. |
| This is why zinc is used, we want it to erode away | | | | Hull plates are usually found on the stern of the boat. |
| and protect the other metal in contact with sea | | | | Tip: If you spot "green" bronze fittings, the bonding |
| water. | | | | has failed and corrosion is in progress. Check and |
| Zincs should be replaced when about half of the | | | | restore the bonding. |
| anode has been lost to corrosion. Ideally we want | | | | Boat Cooling Water |
| that to occur not more frequently than annually. I | | | | Heat exchangers and engine raw water systems are |
| check my yacht zincs routinely and replace zincs that | | | | also at risk. Most heat exchangers are fitted with a |
| need it. At haul out, a full set is always installed. All | | | | zinc "pencil". You will find it under a brass plug. The |
| zincs are not made the same. Insist on MIL spec | | | | pencil is unscrewed from the plug for replacement. In |
| zincs. There is a supplier on my Links page that I get | | | | addition, your transmission and oil coolers will be fitted |
| mine from. Good zincs, good price. | | | | with pencil zincs as well. |