Boat manufacturers often use various types of metal in the construction of boat components, docking hardware, and other boating equipment. When two different types of metals that are in contact with each other are immersed in seawater, some current flows between the metals. The current consists of electrons that are supplied by the active metal in the form of ions. As the metal gives up bits of itself to the seawater, it begins to wear away through a process known as galvanic corrosion. Galvanic corrosion can destroy metal parts of boats and equipment if it is left unchecked.
The use of metal parts in the manufacture of boats is inevitable. Sacrificial anodes can be used to protect different metals from corroding when exposed to seawater. Here is more about galvanic corrosion and how to use sacrificial anodes to protect your boat's metal parts.
The basics of galvanic corrosion
Metals are usually classified into two based on their voltage potential and reactivity. These are the active anodes which have a high voltage potential and tendency to corrode, and cathodes which are passive and less susceptible to corrosion. Active metals include stainless steel, while passive ones include aluminum, bronze, and zinc among others. In a galvanic reaction to occur between the metals, the following conditions must be present:
• There must be two dissimilar metals.
• The metals must be in contact with each other.
• The metals must come into contact with an electrolyte such as seawater.
The use of sacrificial anodes
Sacrificial anodes are metals that are inexpensive and less noble compared to all other metals used on the boat. They are electrically connected or bolted to the active metals on the boat to protect them from galvanic corrosion. Sacrificial anodes are usually made from aluminum, zinc, or magnesium metals. Sacrificial anodes can extend the life of your boat's components by protecting them from the effects of galvanic corrosion.
Placement of sacrificial anodes
Correct positioning of the sacrificial anodes is essential in determining the level of protection offered to the metal parts. For the best protection, the anodes should be fitted to underwater metal parts such as the propeller, propeller shafts, and the hull. Ensure that the parts are painted and finished as required before fixing the sacrificial anodes. Use galvanized mild steel set bolts to fit the anodes onto the metal parts.
Replacement of sacrificial anodes
When exposed to seawater, sacrificial anodes will begin to corrode, and they should be replaced for continuous protection. Ideally, you should replace the anodes when they are at least half dissolved. The period after which you should replace them will vary depending on the frequency of exposure to corrosive elements.
Galvanic corrosion can cause expensive damages to your boat's metal components. However, by using sacrificial anodes, you can protect your investment from these effects and prolong the life of the vessel.