How to Protect Your Boat from Saltwater Corrosion

After investing in your vessel, you want to do everything possible to preserve it and ensure it functions optimally. Right?

Well, every minute your boat spends in the ocean, a different kind of work is happening. Saltwater corrosion is a silent enemy – and it doesn't discriminate. Unfortunately, saltwater causes metal to corrode, pitting your props and slowly turning your beautiful vessel into a costly repair bill.

However, with the right game plan and a little know-how, you can protect your investment and keep your boat in optimal shape for years to come.

Understanding Saltwater Corrosion

The salt and minerals in saltwater allow it to conduct electricity. And when you put a boat with dissimilar metals — say, an aluminum outdrive next to a bronze propeller — in it, the saltwater essentially creates a sort of battery. This is called galvanic corrosion, where the less noble metal starts to corrode to protect the other.

Simple rust is a constant threat, and if you splash metal surfaces with salt water, then let it dry, it leaves salt crystals behind. Unfortunately, those crystals draw moisture from the air, thereby furthering corrosion.

Rust affects everything on your boat – from the engine down to a simple screw. It's sneaky, and that's why boat corrosion prevention is so important.

Preventative Maintenance is Key

Your best defense is to rinse your boat with fresh water after every saltwater trip. As simple as it sounds, preventing corrosion starts with a hose.

Rinse the Boat: Scrub every surface with an effective boat soap and a soft brush: the deck, the railings, the hatches — everything. You need to physically wash that salt off before it can start its dirty work.
Flush the Engine: This is non-negotiable. Your engine has saltwater running through it to keep it cool, and if you don't flush it, the salt will sit there and corrode the internal metal parts.

Most outboards have a built-in flush port. Just hook up a hose and let it run for 10-15 minutes. This simple act of flushing is the number one way to prevent internal corrosion and maintain your engine's health in the long term.

The Heavy Artillery: Deeper Protection

Once you've got the simple stuff down, you can further protect your boat:

Zincs. Remember talking about galvanic corrosion? Well, a sacrificial anode, or "zinc," is the solution.

Essentially, you bolt these little pieces of metal onto your boat hull, engine, and props. And because they're a "weaker" metal, they get eaten away first – sacrificing themselves to protect the more expensive parts of your boat. Just check them regularly and remember to replace them when they're about halfway gone.

Protective Coatings. A quality marine wax will create a protective layer that physically blocks salt and water. Consider using a corrosion inhibitor or spray to create a barrier for your hull, metal parts, and electronics.

Material & Equipment Choices

When you're outfitting your boat or replacing parts, it pays to be picky. Select materials that are specifically designed to withstand corrosive environments. And know that marine-grade stainless steel is the standard for a reason – it provides a tough oxide layer that keeps rust from setting in.

Additionally, most boats are made of marine-grade aluminum. Because of the danger of dissimilar metals (see above), you'll want to make sure that every metal part attached to your hull is properly isolated.

Additionally, apply a challenging, corrosion-resistant paint to the hull and/or metal parts for an added layer of protection.

Electrical System Protection

As we've mentioned, electricity and saltwater don't mix well. That's why a faulty electrical system can cause significant trouble. A stray current from a bad ground can turn your entire boat into a battery in the water, and that kind of uncontrolled galvanic corrosion eats away at your zincs and metal parts at an alarming rate.

That's where a bonding system comes in. A proper bonding system connects all the metal parts of your boat — from the engine to the thru-hulls — to ensure they have the same electrical potential. This prevents current from jumping between them and corroding your rig.

The Smart Boater's Checklist

To stay ahead of the game, you need a routine. Here's your anti-corrosion checklist:

After Every Trip. Rinse everything with fresh water, flush the engine, and wipe down all metal parts.
Every Few Months. Inspect your zincs and replace them if they're looking worn down. Check your propeller for any pitting or signs of damage.
Seasonally. Haul the boat out of the water and do a full inspection. Look for any bubbling paint on the hull or signs of corrosion below the waterline. We also recommend giving your rig a fresh coat of wax.

When to Call a Pro for Help

If you see signs of advanced corrosion, it's time to call in the pros. Here are some red flags to watch for:

Bubbling or Blistering Paint. Blisters forming under the paint on your hull (especially if it's aluminum) are a huge red flag. It means that the corrosion underneath is literally pushing the paint off your rig.
Pitting and Flaking. Check your propeller, shafts, and outdrive. If they're pitted like an old golf ball or if the metal is flaking away, you have a major corrosion problem. This isn't normal wear and tear – it means the metal is being actively eaten away.
Zincs Disappearing Too Fast. While the sacrificial anodes are supposed to erode over time, you should be worried if they disappear at an alarming rate. If you check your zincs a month after installation and they're already halfway gone, it's time to call in the pros. There's likely a stray electrical current in the water that's conducting electricity and accelerating the corrosion process.
Persistent Electrical Issues. If you're experiencing strange electrical issues — such as flickering lights, blown fuses, or a battery that won't hold a charge even when everything else appears to be fine — it could be a sign of a grounding issue or a stray current. (As we mentioned, that's often a root cause of severe corrosion.)

If you notice any of these signs of saltwater corrosion, a marine surveyor or an electrician can identify the source of the problem and make necessary repairs.

Winterizing a Saltwater Boat

Unfortunately, you can't just pull your rig out of the water and walk away when the season ends. Here's how to winterize a saltwater boat:

Step 1: Get your Boat Out of the Water

First things first, you've got to get your boat out of the water and onto a trailer or lift. You can store your boat in your driveway, backyard, or garage; in a marina or boat yard; or in a self-storage facility.

Step 2: Winterize Your Engine

Next, you'll want to winterize your engine. Flush the cooling system to clear out all the salt water, which helps prevent internal corrosion while your boat is sitting idle. Then, we recommend running a special antifreeze or corrosion inhibitor through the engine. This will protect the internal components from rust and freezing.

Step 3: Check the Fuel System

We always recommend filling your fuel tank and adding a stabilizer before winterizing your boat. This will prevent moisture from entering and causing rust.

Step 4: Take Care of the Little Things

Last — but certainly not least — you'll want to remember to:

Disconnect your batteries and store them in a cool, dry place. Unfortunately, a freezing battery is a dead battery. It can also corrode the terminals.
Ensure the boat is spotless before covering it. This prevents mold and mildew from setting in over the winter.