ENGINE HEALTH

and sustain some significant damage to various metal or even problem, however AC current under certain circumstances can wooden parts. be just as devastating. Poor, broken, or non-existent grounds Yes, I said wooden! Through the process called electrolytic are a primary source for stray current. Aside from possibly delignification, current flow can literally eat away at the lignin, providing a fatal electrical shock, the grounding issues will that gooey substance joining the cellulose fibers. As the current definitely create the opportunity for galvanic . The flows through the electrolyte, some of the water gets broken grounds and connections of not only your boat but also any down freeing up some hydrogen and oxygen molecules plus dock or marina equipment are all potential sources for stray some Sodium molecules coming from the salt in the water, current. Remember, water is a very efficient conductor. so we now have Na, H, and O available in close proximity. By Bill Hancock Using a bit of chemistry knowledge, these elements provide Assistant Editor the ingredients to make Sodium Hydroxide. Paper mills use Notice the the Sodium Hydroxide as an electrolytic solution to “cook the Anodes placed wood” in the pulp making process. Logs are stripped of their on each end of As boat owners, we have often anytime your boat is in the water. To bark, chipped and dumped into a vat which contains high the sterndrive Nobility Chart cylinders used to witnessed the results of galvanic lessen the effects of galvanic corrosion, temperature electrolyte called cooking liquor. Suffice it to say raise and lower the Cathode End that when the lignin is dissolved and removed, leaving the corrosion on our various metal parts. It boat owners have traditionally used unit in and out of may surprise you to know that the wood small lumps of sacrificial metal such as cellulose fibers, wood is broken down into pulp in very short the water! on our boats can also be affected through zinc placed at strategic locations like the Platinum order. Wooden boats have been known to have wooden parts a similar process called electrolytic rudder. The corrosion will follow the Golds dissolve in a matter of months under the right conditions. delignification. Let’s explore these topics path of least resistance, so as corrosion Silver Nickel Granted, it is quite uncommon, but nonetheless it does occur. Here are two excellent references for further reading: USCG and more importantly, review the steps occurs, the zinc having the lesser nobility Stainless Steel 400 series You will also notice that the current corrodes the wood paper NVIC 7-95, USDA Research paper FPL 229, provided by Silicon Bronze we should take to prevent them. Let’s simply erodes, thus saving the important around the metal fasteners, making it soft and hence reducing Sunnyland Member, Alan Weinstein. Copper begin by defining the process: parts. Hence, zinc is the metal of choice the function of the fastener. The USCG and the US Forestry Tin Happy Boating to each and every one of you Galvanic Corrosion is an and can be purchased at various marine service both have excellent information on this topic. This is Low alloy steel and stay away from “stray power” – it may eat electrochemical reaction in which stores in a variety of convenient shapes a particularly important example of what can be found in the Cast your boat alive! electrons flow from one metal to a and sizes. Coast Guard report: Aluminum Alloys different metal based on the metal’s is a term that is On wooden boats, bonding systems can cause unexpected Zinc nobility. Now you may ask “what is often misused to indicate galvanic problems. First, by connecting together a number of underwater Nobility”? Think of high nobility as the corrosion. In fact, it is just the opposite. fittings and fastenings, the bonding system may provide the property which makes it very difficult to Electrolysis is the name given to the Anode End metallic links which turn otherwise isolated dissimilar metals into loosen an electron from the metal. The process of chemical changes occurring a galvanic cell. Second, the bonding system often inadvertently supplies unneeded or unwanted to objects higher the “Nobility”, the less potential in a solution or electrolyte due to Harris Chain of Lakes Towing and Recovery for corrosion. current flow. Hydrogen is produced connected to the bonding system by connecting those objects to Metals are ranked on the nobility by electrolysis using electrical current the propeller shaft’s sacrificial zinc anode. This cathodic protection chart with the most noble metals being to split the Hydrogen atoms from the of underwater metal hull fittings often causes damaging alkali Captain John Davis platinum and gold followed by stainless Oxygen atom in water. delignification of the surrounding wood. Membership and Unlimited Towing Services So, what can we do to prevent to effects of galvanic corrosion steel and bronze. In the bottom of the For the most part, galvanic corrosion Photo of a Magnesium Anode – These are MAPS • REFERRALS • FUEL • BOAT SLIPS or electrolytic delignification? ranking, we find aluminum, zinc, and has the greatest effect on boats which readily available at West Marine [email protected] (407) 929-2740 finally magnesium which is the least are kept in the water and have current First and foremost, make sure that both your electrical your dock to ensure that everything is BoatU.S. 24 Hr. Dispatch (800) 391-4869 VHF CH 16 TowBoatU.S. noble. flowing through them while at rest. system and your equipment is designed for marine application properly grounded and there are no stray If you place the two different metals This current is created by improperly and properly maintained. Attach zincs in the recommended electrons. If you go on a cruise and moor in an electrolyte, which in our case is grounded or bonded electrical areas, especially if you are in or near saltwater. Utilize a UL at a marina around other boats, you may water, current flows between the two equipment such as battery chargers and approved galvanic isolator and check your boat for stray current metals. (Note; unless the water is pure, bilge pumps. If, like so many of us, you find your boat stuck between two boats flow if you keep your boat in the water. This is especially it is a conductor, so brackish water, store your boat inside on a trailer with which have some “electrical leaks”. These important if you supply shore power to your boat while it is in saltwater, and even polluted “fresh water” a dry bilge and everything electrical seemingly innocent yachts, typically the water or if it is on a lift where the rudder or prop is even are all excellent conductors.) As the turned off, you will probably be OK. On connected by a common ground through touching the water. Routinely remove the various grounds and current flows, the electrons are released the other hand, if you moor your boat the marina’s power grid, may have clean the connections to ensure conductivity. There are two and, in some cases, plated to another in the water, it may be subjected to stray created enough electrical current flow to crucial sets of grounds; those in your boat and those associated metal. The corrosion occurs at the anode electrons resulting from a faulty circuit. seriously affect your boat in a very short with your shore power. of this galvanic cell. Barring preventative Do yourself and your boat a favor, have time frame. Your boat, in as little as a few Have a certified technician with corrosion control training measures, galvanic corrosion takes place a certified technician run a check on weeks, may become the unwitting anode do the checks. Most people assume that only DC current is a

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