How to Stop Marine Rust & Corrosion

There’s one word that strikes fear into the heart of novice and seasoned boaters alike: rust. If you’ve seen marine rust on your boat and/or boat trailer, you know that the lifespan of your boat is shortening by the day. As a threat to all parts of your boat – the exterior, the interior, outboard, fuel system, and trailer – rust must be dealt with immediately before it leads to mechanical failure both in places you can see and areas that are out of sight. That’s why boat rust prevention is so important.

Luckily, you can take plenty of preventative steps to prevent rust from developing on your boat and trailer and some time-tested steps to prevent rust when you’ve already discovered those all-too-familiar dark-orange streaks.

In this guide, we’ll take a look at several topics related to boat rust prevention, including:

What are Marine Rust and Corrosion?
Common Types of Corrosion in Boats and on Trailers
Where are Rust and Corrosion Most Likely to Form on Your Boat and Trailer?
How to Prevent Rust and Corrosion on Boats and Boat Trailers
How to Remove Rust from a Boat and Boat Trailer
Recommended Products for Boat Rust Prevention

What are Marine Rust and Corrosion?

Before we get into boat rust prevention, it’s important to understand what the terms “rust” and “corrosion” actually are:

Rust is the name given to iron oxide (Fe²O³), a typically reddish-brown oxide formed by the reaction of oxygen and iron in the catalytic presence of air moisture, or water. Rust occurs in ferrous metals, with iron as part of its composition.

For most boats, iron-containing (ferrous) metals are used for their strength and relative lightweight. However, the proximity to water and humidity eventually corrodes these materials for boats and trailers over time, requiring preventative measures and replacement to keep them seaworthy.

Corrosion, on the other hand, refers to the process of metals being chemically destroyed or worn down by chemical reactions. Rust is a type of corrosion, but it is not the only type of corrosion that affects boats and boat trailers.

Common Types of Corrosion in Boats and on Boat Trailers

Several types of corrosion commonly occur in boats and trailers. As you examine your boat for signs of corrosion, try to identify which kind of corrosion is happening to help you troubleshoot where it’s coming from and how to prevent it.

Atmospheric Corrosion

When metal is exposed to the air that contains moisture and salt

Immersion Corrosion

Metal in water accelerates the corrosion process – especially in warm saltwater.

Galvanic Corrosion

This type of corrosion occurs when dissimilar metals are immersed in a conductive solution (water, saltwater) and are electrically connected. The metal that is more resistant to corrosion (the noble metal) “steals” mass from the other metals (less noble). Mass transfer occurs in the electrolyte (water) – which explains the purpose of sacrificial anodes in outboard and sterndrive motors.

Pitting Corrosion

Pitting corrosion is a localized form where tiny holes and cavities are produced in metals. Because these holes start small when they first occur, this corrosion can be difficult to detect on boats and trailers.

Poultice Corrosion

Poultice corrosion occurs when a metal is covered by absorbent materials, dirt, and debris, trapping moisture against the unprotected metal surface. This is most commonly seen with painted aluminum with water trapped under the paint or butted up against plywood, such as an aluminum fuel tank.

Erosion Corrosion

The constant velocity of moving water gradually wears away the metal. A boat’s trim tab is most likely to experience erosion corrosion.

Stress Corrosion

Hairline cracks can form for metal fittings that have been formed through bending or metal working, eventually branching out from the main crack. As the material weakens through corrosion, these branches – resembling a tree without leaves – spread further and further until eventually breaking under load or pressure.

Where are Rust and Corrosion Most Likely to Form on Your Boat and Trailer?

The most common spots of marine rust and corrosion forming on your boat include:

Sacrificial Anodes
Transom Bracket Anodes
Propeller
Cylinder Heads
Fasteners (Bolts, Nuts, And Other Connections)
Ladders
Cleats
Handrails
Aluminum Fuel Tanks
Battery Terminals
Beneath Painted Surfaces
Terminal Strips
Fuse Panels
Circuit Breakers
Electronics
Running Lights
Alternator Leads
Reefer Unit Wheels & Hubs
And other metal components on the boat

The most vulnerable parts of a boat trailer to marine rust and corrosion include:

Leaf Springs
Fasteners (including Bolts, Nuts, Washers, and other connections)
Wheel Bearings
Brakes
Bunks
The Frame (watch this video for a novel approach to coat the interior of the frame with rust protection)
And other metal components on the trailer

How to Prevent Rust and Corrosion on Boats and Boat Trailers

Now that you’re aware of where rust and corrosion most commonly occur on your boat and boat trailer, it’s time to learn about several methods for boat rust prevention.

Visually inspect your trailer and boat often.

Rust and corrosion are progressive, often starting with small signs that are visible with a brief inspection. It’s important to inspect your boat when it is out of storage on a biweekly or monthly basis so that you can spot corrosion and address it before it spreads and eventually leads to mechanical failure.

Hose down your boat and trailer with fresh water after every usage

It’s extremely important to hose down your boat and boat trailer with fresh water after every use. Hosing with fresh water helps remove salt deposits, dirt, and debris that contribute to further corrosion. Be sure to aim for hard-to-reach places and adequately dry any areas where moisture can accumulate.

Use a salt-removing product if you boat in salt water

In addition to washing your boat with fresh water, it’s important to use anti-corrosion products – especially if your boat has been in salt water. Products like Star brite’s Salt Off are designed to break up hard-to-remove salt deposits and other grime that has bonded to your boat’s hull and metal components. Many brands also contain special polymers that bond to the treated surface to help prevent the formation of future deposits.

If you boat in salt water, then it’s highly recommended that you use salt-removing products after each trip.

Note: Always verify if the salt-removing product is designed to be safe for your boat’s hull material (ie. gelcoats).

Apply sealants on the trailer and boat before launching your boat

It’s important to regularly seal the vulnerable spots on the boat and trailer to prevent corrosion. Popular sealants prevent water from passing through them, preventing corrosion that would otherwise react with the bare exposed metal. For many exposed metal components on your trailer, WD-40 is an appropriate sealant, whereas boat components require a more heavy-duty product suited to immersion in the water.

After thoroughly cleaning your boat, simply apply a generous amount of sealant and wipe away any excess. Be sure that the surface is completely dry and debris-free, as the sealant may not completely adhere.

Remember that these products eventually wash away when your boat and trailer are exposed to the water, so you’ll need to apply them periodically. Similarly, rough cleaning will also wash them away, so you may want to apply a sealant as part of your regular cleaning regimen.

Apply marine-grade paint to exposed metal surfaces

Marine-grade paint serves the same purpose as sealants and surface lubricants, like WD-40. Depending on the type of trailer type you have (steel or aluminum), apply the appropriate paint to your boat trailer.

Paint, however, needs a few words of warning: First, don’t use any non-marine-grade paint you have around the house. These paints are often porous or can trap water beneath the painted surface, causing internal corrosion you won’t see until it’s too late. Second, don’t use paint to cover up corrosion, as these materials can start to weaken through mechanical fatigue and eventually fail when you need them the most.

Always store your boat trailer in a dry place.

Adequate storage is extremely important. Even if you constantly wash your boat, the storage location must be in a dry place.

When your boat and trailer aren’t in the water, keep them away from all sources of moisture. This includes areas of your home or storage area prone to water pools. Also, avoid storing your boat over grass and foliage, as the morning dew and drying throughout the day can accelerate corrosion. Instead, choose concrete, blacktop, or fast-draining gravel to protect your boat from rust.

How to Remove Rust from a Boat and Boat Trailer

Even after taking all precautionary measures, you may still have to deal with rust on your trailer and boat’s metal components. The following are a few procedures to remove the rust.

Scrub the rusted surfaces with a wire brush

If rust is spotted soon enough, you can actually remove marine rust with a wire brush to get the metal down to an uncorroded surface. Before starting the process, ensure that the rusted surfaces are completely dry.

Once dry, gently brush the surface with a wire brush back and forth, being careful not to strip nearby surfaces. If you have a drill, you can buy a wire brush attachment, and you can scrub the rusted parts. Most experienced DIY boaters use both the wire brush and the drill attachment, as the brush can go to rusted places where the drill can’t go, and vice versa. Always wear adequate eye, mouth, and hand protection, as tiny rusted bits can cause irritation and even tetanus, a serious disease that’s caused by the bacteria in the rust.

Once the rust is completely removed, apply an anti-rust/corrosion product before repainting any affected components.

Replace any rusted components

Rust strips metals away from parts, so there may be some parts that need to be completely replaced instead of brushed away.

Removal of rusted parts, however, can be an issue, as the oxidation process of corrosion may have softened the surrounding metals, creating hard-to-remove bonds that require drilling the old material out. For example, a corroded bolt may require not only the removal of the bolt but also a rethreading for a snug, water-tight fitting.

Recommended Products for Boat Rust Prevention

Consult your owner’s manual and product label to determine which products are right for your boat and trailer.

As you can see, following some simple preventative maintenance extend the life of their boat and trailer. When marine rust and corrosion are spotted, addressing the cause and stopping the spread ensures that you’ll spend less time worrying and more time enjoying your time out on the water.

PartsVu has plenty of products to help boaters keep their boat and trailer in tip-top shape and prevent marine rust and corrosion. Shop today and boat rust-free!