The effective use of zinc anodes is an extremely important part of properly caring for and maintaining your boat. However there are a lot of boat owners that don't really understand why zinc anodes are used and how anodes work. Because of this, we've compiled some basic information about anodes.
Whenever two metals contact each other in salt water, a current flows between those metals. The electrons that make up the electrical current are taken from one of the metals, causing the metal to corrode. By purposely attaching a metal that is less noble (in this case, an anode) than the boats parts, you can protect critical portions of your vessel at the expense of the cheaper zinc. This is why anodes are often called "sacrificial anodes."
Propellers, shafts, rudders, struts, etc., can be cathodically protected at the expense of these sacrificial anodes. Here is an example of galvanic corrosion damage caused by NOT having good functioning anodes:
Propeller damaged from non replacement of zincs
This is why we stress the importance of checking the percentage of "life" left in your existing zincs and recommend a maintenance program to keep your boat from getting damaged. Our procedure for zinc replacement is to prepare the contact area by ensuring it is very clean and free of contaminants: We use black abrasive 3M Scotchbrite pads and paint scrapers when necessary. We use a pneumatic wrench which runs off our air to ensure zinc contact is tight and we use pressed fit zincs. At Double J Diving we are able to offer customized Zincs and we exclusively use zincs that are manufactured in the USA. Here is a link to Sea Shield Marine (our primary Zinc manufacturer.)
Proudly embracing American made product.
A note about recycling. As part of our regular service we handle the recycling of all replaced anodes.
For further information, Click Here to view an article on the subject by Don Casey. (Please Note: This article suggests that zincs should last a year. In our local waters we have NOT found this be true.)