Corrosion is caused when metals are exposed to water. So, in short, corrosion is something all boaters will have to deal with at some point in time, but there are ways to slow it down. Your level of preparation will determine how frequently you’ll need to deal with corrosion throughout your boat’s life.
Let’s break down the different types of corrosion that can affect your boat and what to do about them, so you can keep your custom powerboat in tip-top shape.
What Is Corrosion?
Basically, corrosion is metal trying to revert back to its original condition.
When iron is mined from the ground, it’s essentially useless red-brown powder. But, when refined, it turns into a strong metal that can be used to make steel and all sorts of applications—like building components for custom powerboats.
Over time, the atoms in the iron want to return to their normal state as red-brown dust. Electrochemical reactions caused by oxygen (which is found in water) speed up the process. That’s why if you leave an iron tool outside in the rain for too long, it’ll start to rust (which is a type of corrosion).
Different metals corrode at different rates. The more active a metal is, the faster it’ll corrode. Here are a few common metals ranked from least to most active:
- Stainless steel
This is why a gold wedding band won’t corrode, even if you wear it in the shower, but an iron hinge will start to rust in the backyard very quickly. Gold is less active than iron. Of course, from a cost perspective, you probably don’t want gold components on your boat, but a stainless-steel prop will resist corrosion much better than one made of aluminum.
Types of Corrosion
The type of metal isn’t the only thing that will determine how fast corrosion occurs. The type of corrosion will also play a large role in how fast the process takes place. There are three types of corrosion boaters should be most worried about:
Galvanic corrosion happens when two different metals are grounded (meaning connected by a wire or touching) and immersed in a conductive solution. Electricity—which is the underlying cause of corrosion—flows from the more active metal to the less active metal. The electricity flowing from the more active metal ionizes the atoms, causing them to oxidize and corrode.
Since that sounds super technical, let’s look at it from a boating perspective.
Your custom powerboat is made of many different metals. For example, you might have an aluminum lower unit and a stainless-steel prop. When your boat is in the water (a conductive solution), the more active metal (aluminum) will send an electrical current to the less active metal (stainless steel), causing the aluminum to corrode.
Electrolytic or Stray Current Corrosion
Electrolytic or stray current corrosion works similarly to galvanic corrosion but on steroids. It’s the fastest type of corrosion and can eat away at your custom powerboat’s metal components in a matter of days or even hours.
This type of corrosion happens when metal is actively charged with electricity. One of the most common examples of stray current corrosion is if your boat’s battery components aren’t properly insulated or connected.
The power from the battery can enter your boat’s metal components, go through the conductive solution (the water), and connect to a ground (like a metal pier). With the added electrical output, the corrosion of your metal components happens much faster than standard galvanic corrosion.
For this type of corrosion, the type of metal doesn’t really matter. Stray current corrosion can affect any type of metal, even your stainless-steel props.
Crevice corrosion is a type of corrosion that mostly affects stainless steel, a “rustproof” metal.
Stainless steel doesn’t rust because of a thin layer of chrome oxide that covers the surface of the metal. If moisture gets trapped in a small space (crevice) touching the stainless steel and creates a stagnant zone of water, it’ll deprive the chrome oxide protection of oxygen and break it down. When the protective layer is gone, the stainless steel will rust just like any other metal.
Tips to Avoid Corrosion
For standard electrochemical corrosion, the type that just happens over time, you don’t have to worry too much. It’s the slowest form of corrosion and can take decades to hurt the integrity of the metal.
The best way to fight basic corrosion is to paint metal surfaces. The paint adheres to the surface of the metal, preventing oxygen from reaching the metal and stopping basic corrosion from the air and water. Keep your paint fresh and follow all general maintenance guidelines to keep your metal surfaces from basic rusting.
Unfortunately, a fresh paint job won’t do much to protect your metal components from galvanic and stray current corrosion. For that, you need sacrificial anodes.
Sacrificial anodes are metal pieces connected to the boat’s electrical system that are more active than all the other metals in the boat. When galvanic or stray current corrosion is present, the sacrificial anodes accept all the electrical currents, keeping your more important custom powerboat parts protected. They literally sacrifice themselves for the good of the boat!
Most sacrificial anodes are made out of zinc or magnesium, two highly active metals. In fact, you might hear sacrificial anodes called “zincs,” since that’s the most common material. These metals are much more active than any other metal used in the boat, so they accept all the electrochemical corrosion.
Because they’re designed to corrode, it’s important for boat owners to keep a close eye on their sacrificial anodes. If they become too corroded, they could stop protecting your other components. Check all your sacrificial anodes at least annually and replace any that are half depleted.
Protect Your Custom Powerboat from Corrosion
Unfortunately, there’s no way to avoid corrosion completely, but there are ways to keep it at bay. Use components made of less active metals, maintain your paint job, and make sure sacrificial anodes are in good condition. Keeping corrosion protection in mind, your custom powerboat can be rust-free for decades.
If you’re ready to get into the exciting world of boat ownership, the experts at Mystic are ready to help. We build high-end custom powerboats that are specifically designed with your tastes and preferences in mind. Contact us to schedule a one-on-one meeting to discuss your needs today!