Boater's World is your Sacrificial Anode Center. We want to make sure engine troubles don't keep you from having fun on the water! No matter where you choose to do your boating, we have all the right products to help take care of your boat. Read this quick overview on how to protect you engine from corrosion!
What causes corrosion? Seawater is a good conductor and freshwater a bad conductor, so corrosion is worse in seawater. Generally, corrosion rates increase in proportion to the amount of oxygen in the water. However, cracks and crevices, which are areas starved of oxygen, become anodic and corrode also. Higher temperature increases corrosion rates - doubling for every 30 degrees C 55 degrees F. There are various types of microorganisms that can contribute to corrosion, either by removing protection or causing a corrosive environment.
Why do I need anodes? You need anodes on your engine because when two different metals are in contact, electrons will flow from the more negatively charged metal anode to the more positive metal cathode. If you want to protect both types of metal from corrosion, you must add a third metal such as zinc, although magnesium and aluminum are also used. This active metal becomes the anode for both metals. The zinc or aluminum sacrifices itself to protect the other two metals, hence the term "sacrificial anode".
Do's and Don'ts
DO change your anode when they are 50 percent corroded DO make sure they make good electrical contact - remove paint and clean the mounting surface. DO protect trim tabs individually do not bond. Although they are usually made from stainless steel they can still corrode and need sacrificial anodes. DO be sure to use new fasteners on sterndrives - even stainless bolts fail as a result of corrosion. DO keep a sterndrive immersed in the water so that the anodes can work. DON'T use zinc anodes on aluminum outdrives DON'T paint anodes. They will not 
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