Many boats, specifically pontoons, have an aluminum construction which tends to be corrosive resistant, but not corrosion proof. There’s a difference. In this short guide I am going to discuss pontoon boat electrolysis plus how to stop electrolysis on a pontoon boat.
Please be aware, I’ve never had to do this myself, as I’ve not suffered with pontoon boat electrolysis. I’ve looked up all the various prevention tips I can find online. This article was contributed by another pontoon boat owner.
The different types of corrosion
There are different types of corrosion, especially galvanic corrosion, and electrolysis due to metals being in electrolytic solutions, that affect aluminum pontoons and different ways in resolving this common problem.
Galvanic corrosion is one of the most common ways in which aluminum pontoon boats experience corrosion, especially in salt water.
Electrolysis can occur when electricity flows through the metal parts of your boats, affecting the various systems which help power the boat. There are different ways you can help prevent this from happening.
When two metals are touching each other or are electrically connected by a conductor, and then are immersed in an electrically conductive fluid, such as salt water, an electro-chemical reaction may occur.
Galvanic corrosion is more prevalent when using the pontoon boat in salt water, however it still does occur in freshwater.
Saltwater is an electrically conductive solution, meaning that when a metal is contact with it, it will lose atoms and will begin to corrode.
One of the best ways to prevent corrosion due to galvanic corrosion is by making sure you do not leave your boat at traditional docks which leave the boat in water when it is not in use. In order to prevent the corrosion, the metal of the boat must not be touching water.
While you can use a tradition boat lift, they often require a power source to use, which also requires additional maintenance and plug in sources near the dock.
Floating boat lifts solves both problems, by not having the boat sit in the water when it is not in use and it also does not require a power source.
Using a floating lift will also save you time and money by not having to haul the boat into and out of the water when you need to clean or repaint it.
It saves you money by not needing a power source.
Types of floating boat lifts:
- Static Floating Boat Lifts
- Air Assisted Floating Boat lifts
- Multi-hull Floating Boat Lifts
If you are interested in pontoon boat lifts, here are some related articles including more detailed information:
- How much pontoon boat lifts cost
- How to perform a pontoon boat lift conversion
- A buyer’s guide to pontoon boat lifts
- Some pontoon boat lift reviews
Preventing galvanic corrosion with zinc anodes
Types of sacrificial anodes:
- Magnesium- for freshwater
Sacrificial anodes are highly active metals used to prevent less active metals such as aluminum, from corroding. They are created from a metal alloy with a more negative electrochemical potential than the other metal.
Breaking the electrical connection between two exposed metals by connecting them to another anode will prevent galvanic corrosion.
This anode is usually inexpensive and is connected, bolted, or wired into electrical contact with another metal.
These anodes extend the life of the boat’s hull, engine, rudder, propeller shaft, engine cooling system, refrigeration condenser, and other metal components by protecting them from any deterioration.
Zinc is not as active as aluminum, and so having zinc anodes electrically attached to the aluminum parts will help to protect the boat amd prevent pontoon boat electrolysis.
The zinc gives the aluminum extra electrodes to shed rather than aluminum shedding its own, therefore corroding the zinc before the aluminum.
It is important that you do not add too many zinc anodes, because too many will cause the zinc to develop crust and it will then stop preventing the aluminum from corroding by not corroding at all and creating a barrier.
How to add the zinc:
- Place a silver electrode near the item that needs to be protected
- Touch the positive probe and note the meter’s reading
- Connect a sacrificial zinc to the metal needed to be protected
- Protection is adequate when the new voltage is 0.20 volts
Other methods for preventing corrosion
If purchasing a new floating boat lift is not in your budget or you’re not too sure as to how to attach different anode electrodes, there are still a variety of other ways you can prevent corrosion on your boat.
- It is very important to repair any cracks and scratches that expose bare aluminum, as soon as they come about. The exposed aluminum will then have a chance to interact with water and begin to corrode, as well as any parts near it.
- Do not mix metals. Metals touching other metals, allows for corrosion to occur in a similar manner as salt water does. It allows for the exchange of atoms, since each metal is electrically conductive, and so it is important to make sure that other metals are not touching the aluminum. Mixing of metals can be reduced by isolating connections between them. Manufacturers usually take care of isolating most of these connections, but you can still check to ensure that there are not any left.
- Using paint and coatings that are designed for use with aluminum is also important and helps prevent corrosion. Much of these paints and coatings provide a barrier between the aluminum boat and salt water. However, do not paint the anodes or grounding plates as this will prevent for basic and necessary reactions to occur. Interlux and Pettit sell aluminum compatible paint systems that are copper free and work well on boats.
- Move at slower speeds. While moving quickly on boats is always a lot of fun, it may be doing more damage to your boat than you think. As speed increases, the waves around the boat get higher and the tubes of the boat may be completely submerged underwater for longer periods of times. When the tubes submerge, waves can crash all over different panels, including the deck of the boat. All these outcomes expose the boat to saltwater and make it vulnerable to corrosion in more areas than it needs to be.
- When you’re done with a day of boating on salt water, wash the boat thoroughly with fresh water from a high-power hose to flush out any trapped salt water and remove dried salt deposits.
- Avoid using lubricants made with graphite aboard the boat.
- Do not use an automotive batter charger above the boat.
- Keep hooks, sinkers, and caps, as well as other metal objects out of the bilge.
- When adding hardware to the boat, try to use aluminum fittings and fastners. If these are hard to find, use 300-series stainless steel and make sure to isolate the fitting with plastic washers or pads. Use polysulfide beddings to keep out water.
- Lastly, it is important to familiarize yourself with the boat’s construction quality in order to effectively prevent it from corroding. Pontoon boats are built in different ways, and depending on their internal deck materials, some may be more exposed and subject to corrosion than others.
This includes making sure that the log tubes are completely welded to the decking that the decks are securely screwed to the frame so that they can handle swells they may encounter.
Some pontoons are also sold as salt water series, which guarantees that the manufacturer has taken additional measures to make the material salt water resistant, but this does not ensure it is completely resistant.
More tips for preventing pontoon boat electrolysis
- Do not exceed 1,300 millivolts of voltage when protecting aluminum
- Properly maintain and conduct various electrolytic tests on all systems
- Periodically test for discoloration at pinholes
Why aluminum is the most used material for pontoon boats
Aluminum is not only inexpensive and easy to manufacture, but it is usually non-corrosive or corrosive resistant when exposed to moisture for long periods of time, making it very durable. Despite its non-corrosive property, rusting may still occur when pontoons are submerged in mud or sand.
Though rusting still occurs, and buying an aluminum pontoon is more expensive than buying pontoons made from other materials, they are still your best option compared to other types of materials because they are travel in water reliably well.
Aluminum pontoons require minimum maintenance and repairs, and provides you with the guarantee of having a boat that will last you longer than other boats. The aluminum material is light weight, increasing their speed and supporting their availability to transport via trailer.
Other pontoon boat materials:
- Fiber Glass
Why should you use magnesium for fresh water and not saltwater?
Fresh water is much less conductive than salt water, therefore magnesium anodes are the best option because they are more active than zinc or aluminum, and so they will protect the parts more effectively.
How to test for pontoon boat electrolysis?
To test if any of your systems have been affected by electrolysis, you will need to test the voltage of the various systems. Attach the negative lead to a ground, the positive lead to the system, and measure the voltage. If the voltage is more than 0.10 V, there is an electrical current flowing through the system.
Does air affect pontoon boat electrolysis?
Above the water line, aluminum does great. When aluminum is exposed to oxygen, it actually develops a film of aluminum oxide that is so dense, it bonds to the metal and acts as a barrier to prevent further corrosion.