Water Resources

Background on Boat Corrosion - March 2024

Summary

The article below describes the reasons for corrosion of boat surfaces.  Some people have questioned whether the use of aquatic herbicides for invasive weed control contributes to accelerated corrosion.  Chemical control of aquatic plants and algae is a common and necessary activity but is highly unlikely to contribute to corrosion of boats due to the rapid dilution and short-lived nature of these treatments.

A more likely reason is “galvanic corrosion”, which is caused by dissimilar metals used on a boat.

The hull of a boat is commonly aluminum, which carries a negative charge, whereas propellers and other boat parts are made of materials that carry positive charges. Water (even freshwater) carries enough electrolytes to create conditions for galvanic corrosion.

A common way to minimize the corrosive effects on boats is to utilize sacrificial anodes made of zinc, aluminum, or magnesium. These anodes absorb the galvanic charges and corrode first, which protects the more valuable metals such as the boat hull or propeller.

The complete article follows.

By Brett Bultemeier - University of Florida

Corrosion or fouling of boat surfaces has been a problem for as long as boats have been used for travel or leisure. From wood decay and barnacle growth on ancient vessels to corrosion of metal on modern boats, there are a host of issues that can damage the integrity of a boat hull. It is not just seafaring vessels that have to contend with corrosion and fouling; many freshwater boats are also subjected to these forces. 

Particularly with the advent of newer materials and disparate metals used in modern boat manufacturing, the process of corrosion continues to be a major problem. Some have questioned whether the use of aquatic herbicides for invasive weed control contributes to accelerated corrosion.

Management of invasive aquatic species (particularly plants and algae) is both necessary and common for many waterbodies throughout the United States. This is often accomplished with the intervention of chemical control (herbicides and algaecides) to remediate these problematic invaders. However, this has led to the common misconception that these chemicals directly cause corrosion or pitting. Though it is possible for these chemicals to be involved in that process, this article will discuss why that is unlikely in most circumstances.

Modern boat hull and propeller construction involves the use of different types of metals that can act as either anodes or cathodes, with negative and positive charges, respectively. The basic formula for a working battery is that electrons from an electrolyte solution (acid for batteries) flow from the anode to the cathode. For those who have seen the corrosion old batteries can cause, this is similar to the galvanization that can occur in boats. 

The hull of a boat is commonly aluminum, which carries a negative charge, whereas propellers and other boat parts are made of materials that carry positive charges. Water carries enough electrolytes (even freshwater) to create conditions for galvanic corrosion. Though saltwater is more commonly associated with this process, freshwater has enough dissolved minerals and particles with a charge to cause corrosion as well. Furthermore, stray current in the water, from powered boat docks or incorrect boat wiring, can further add to the corrosive forces acting on boats in freshwater.

A common way to minimize the corrosive effects on boats is to utilize sacrificial anodes made of zinc, aluminum, or magnesium. These anodes preferentially absorb the charges and corrode first, which protects the more valuable metals such as the boat hull or propeller. This can either be passive or induced (with electricity), but the key piece is that these anodes MUST be in the water in order to work. A boat that is partially submerged in the water will not be effectively protected if the sacrificial anodes are out of the water. If an induced system is at work, then power must be provided, so anodes need a power source.

Alternatively, storing a boat completely out of the water will halt the corrosive process. The sacrificial anodes will wear out with time and need to be replaced. As with any system, proper maintenance and routine checks of the system will keep them functioning at their best. If caught early, damaging corrosion can likely be stopped.

Sometimes aquatic plant and algae management is blamed for causing corrosion of boats in the area of treatments. Although it is true that in their undiluted form these chemicals can be corrosive, these chemicals are greatly diluted into a spray tank before being even further diluted into the lake water. 

Once in the treated water these chemicals are found at very low concentrations, as low as a few parts per billion and even at their highest only a few parts per million. Furthermore, these low concentrations are short lived in the environment due to rapid dilution away from treatment site and environmental breakdown/sequestration. 

This short-lived, low concentration introduction of charge particles to the water is very small compared to the conditions that exist naturally in the lake. If all lakes were pure deionized water, then perhaps these chemicals would be a significant contributor to long-term corrosive action, but in lakes as they exist now, their

contribution to enhanced corrosion is insignificant.

Many people believe that herbicides and algaecides have negative effects on their boat surfaces after they observe a chemical treatment taking place, become concerned about

their boat, check the hull and find corrosion. It is likely that the corrosion was already there but went unnoticed until the boat owner checked the hull in response to seeing the weed management operation. If corrosion from herbicide and algaecide treatments were common, the boats used to apply the treatments would quickly corrode during the

treatments, which is not what happens.

Galvanic corrosion is a common problem for modern boats, even in freshwater systems, and requires constant diligence and maintenance. The use of sacrificial anodes is critical to help protect the valuable metal parts of a boat such as the hull and propeller. Therefore, these anodes must be kept in the water, checked routinely, and constantly energized (if relevant), in order to be effective. Storing the boat slightly out of water such that the anode is not submersed is a common error that can lead to lack of corrosion protection.

Chemical control of aquatic plants and algae is a common and necessary activity but is highly unlikely to contribute to corrosion of boats due to the rapid dilution and short-lived nature of these treatments. Diligent maintenance and routine inspections of the boat and the protective processes (i.e., sacrificial anodes) are the best tools to fight corrosion of boats.

For more in-depth reading see the following websites:

http://www.boatus.com/boattech/articles/marine-corrosion.asp

http://www.boatus.com/boattech/casey/sacrificial-zincs.asp

AERF

Aquatic Ecosystem Restoration Foundation

Pontoon Pitting Update Dec 2023

At our November Board meeting a resident had a concern and questions about pitting on his pontoons and the use of copper sulfate in the lakes as being the cause.

Anyone that has a concern or experienced pitting on their pontoons can take some precautions on their own to help prevent this from happening.

Pitting can be caused by several different factors:

1. 1. Galvanic corrosion can be caused by a stray electrical current in the water from the boat itself, or on shore power.

   2. Contact with dissimilar metals.

   3. Possibly chemicals used in the water for algae treatment, (however this is in a very diluted form).

Two preventive measures are:

1. Installing Sacrificial Anodes to the pontoon.

2. Installing a battery cut off switch when boat is not in use.

I have had very good results using both methods and it has stopped the pitting process on my pontoons.

The website for the anode has bolt on style (which can be mounted to the bracket on a pontoon where a depth finder or speedometer would typically go).  They also have ones that can be hung over the side of the boat when you are docked.  This is the link for a Magnesium Anode: https://boatzincs.com/zhc-2-mg/

The Battery Switch description is: 12V 24V 48V Battery Disconnect Master Cutoff Switch for Marine Boat RV ATV UTV Vehicles, Waterproof Heavy Duty Battery Isolator Switch (On/Off), and the link is: https://a.co/d/ayBGaZ8

Thank you,

Corey O'Higgins, Water Resources 

 Lakewood Village Goose-Swan Update  July 1, 2021 

A meeting was held on Thursday, June 24 2021 to discuss what to do about the aggressive behavior of mute swans towards geese and humans.  This is a summary of that meeting with actions for 2021 and 2022:

Issues

1)      Feeding the waterfowl.  PLEASE DO NOT FEED the waterfowl.  It is unhealthy for them and increases the pollution in our lakes, especially where they are fed.  There are serious problems when humans and waterfowl interact.  See the article in LVIA.net for more info.

2)      Harassing the swans.  PLEASE DO NOT HARASS the swans.  They will remember the harassment and assume that all humans will harass them.  This leads to serious risks for children and adults.

3)      Disturbing the nests and eggs.  PLEASE DO NOT DISTURB existing nests.  This is illegal.

Natural Balance

1)      Living on a lake means that we share an ecosystem with plants and wildlife.

2)      Swans and geese compete for the same territory.

3)      Male swans want to drive away geese to ensure their cygnets are safe.

4)      1-4 pairs of swans will keep the goose population down without any interference from humans.

Facts

1)      Mute swans are not native to Michigan.  Permits can be obtained to remove them.

2)      Trumpeter swans are native to Michigan.  Permits cannot be obtained to remove them.

3)      The swans on Neva and Brendel lakes are mute swans.  Mute swans will compete with Trumpeter swans and drive them away.

5)      Male swans will protect their cygnets until they fledge and fly away (around week 2 of July).

6)      Swans remember all sources of food and all sources of harassment.

2021 Recommended Actions:

1)      Do not feed, harass, or disturb the swans or geese.

2)      Try to avoid the swans if possible. If one approaches, idle your watercraft and wait, do not charge the animal.  The swans will stop being aggressive as soon as their cygnets fledge (about July 14).

3)      Identify and report all nests and harassment to a Water Resources Board member.

4)      We will not take action against the swans this summer.

2022 Recommended Actions:

1)      In late March-April we will encourage the swans to nest away from canals on Brendel.

2)      A permit will be secured to remove mute swans in case they become too numerous.

Hoped-For Results:

1)      Mute swans will continue to keep our lakes free of Trumpeter swans.  Mute swans are controllable, Trumpeter swans cannot be removed under Michigan law.

2)      Mute swans will build future nests away from canals, reducing the need to remove them.

3)      We will not have to pay to remove swans or geese and we can all enjoy our beautiful, natural environment in Lakewood Village.

Please discuss these points with your neighbors.  We all have a role in the solution.

If we each do our part, we can have a great neighborhood with wonderful lakes full of wildlife.