What is electrolysis and how does it affect my boat?

Electrolysis, or stray current corrosion, happens when an electrical current leaks from the boat's wiring, shore power or a nearby boat and leaves your underwater metals through the water, eating them away. It can damage props, drives, shafts, rudder fittings and thru-hulls quickly. Testing finds it early, before the repairs get costly.

How do you test for galvanic corrosion on my boat?

We hang a silver/silver-chloride reference electrode in the water and read the voltage of your underwater metals against it, with shore power connected and disconnected. The readings show whether your anodes are protecting the boat, over-protecting it or not doing enough, and whether stray current is present. We also check every bonding wire and connection for continuity.

How often should I have my boat tested for corrosion?

Have it tested when your anodes wear much faster or slower than usual, after electrical work or a move to a new slip, and as a routine check when the anodes are replaced. Boats that stay in salt water all year benefit most from regular checks.

What’s included in the bonding system check?

We inspect the bonding wires and terminals in the bilge, test continuity from each underwater fitting (thru-hulls, shaft, rudder, struts, engine and drive) to the bonding system, and check that the anodes are connected and wearing as they should.

Do you provide any maintenance after the corrosion testing?

Yes. We repair bonding wires and connections, install galvanic isolators and replace the anodes we can reach, with a written estimate before any repair. Anodes below the waterline on a boat in the water are changed by a diver we refer you to, who works for you directly.

What kind of warranty comes with your testing and services?

Our workmanship is warranted for 90 days from the invoice date, and parts we replace, such as anodes or bonding wires, carry their manufacturer's warranty. Your invoice lists the tests and the work done.

Do you offer any recommendations to prevent corrosion after testing?

Yes, we provide tailored recommendations based on your boat’s condition. These may include installing additional sacrificial anodes, upgrading your bonding system, or using corrosion inhibitors. We also suggest regular checks and cleaning to prevent the buildup of corrosive elements, especially in saltwater environments.

Marine technician lowering a silver-chloride reference electrode into the water to test for stray

Marine technician lowering a silver-chloride reference electrode into the water to test for stray (2)

Electrolysis & Galvanic Corrosion Testing and Bonding System Check

Corrosion of underwater metals often goes unseen until a part fails. If you are burning through zincs or seeing pitting on your prop, we use a silver/silver-chloride reference electrode to find stray current or weak protection, and repair your bonding system where needed before the damage spreads.

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$150 /hr

Labor estimate Usually 1–2 hours

Book sends us a ticket; nothing is charged online. Before any work you get a written estimate for labor, parts and the trip fee, and nothing is done without your OK.

Trip fee By distance, one way: $30 in San Pedro, $50 in Long Beach

San Pedro$30
Wilmington, Terminal Island$40
Long Beach: Shoreline, Rainbow Harbor$50
Long Beach Marina, Alamitos Bay$60
Redondo Beach$60
Seal Beach, Huntington Harbour$75
Marina del Rey$85
Newport Beach$110

Farther away: $25 plus $2.50 a mile, one way from our San Pedro shop. No trip fee when the boat comes to our shop, or for plan members. The work of a visit is at least $150; the trip fee is on top.

Registered in California: Breeze Marine Boat Service LLC, San Pedro
Where we work: At your slip from Marina del Rey to Newport Beach, or in our San Pedro shop
Questions first: (213) 693-0224 or submit a ticket

About this service

Hidden Corrosion

Find Corrosion
Before It Spreads.

Some corrosion is unavoidable on a boat in salt water, but serious damage usually is not. We measure your underwater metals against a reference electrode to check that your bonding system and zinc anodes are actually protecting your props and drives.

The "Half-Cell" Test

We don't guess; we measure. Using a silver-silver chloride (Ag/AgCl) reference electrode, we check the voltage of your underwater metals against the seawater. The reading shows whether your boat is over-protected, under-protected or in the protected range.

Bonding Integrity

On a boat with a bonding system, the underwater metals are connected by green bonding wires to a common bonding conductor and the anodes. A broken wire leaves that propeller, shaft or thru-hull without anode protection, so it can start to corrode. We test continuity across your entire boat bonding system.

Stray Current vs. Galvanic

Galvanic corrosion is slow. Stray current corrosion (electrolysis) can be fast enough to eat a drive in days. We test for DC leaks and install galvanic isolators to block the low-voltage galvanic current that travels along the shore-power ground wire.

The Science of Protection.

A rigorous diagnostic protocol.

Reference Test

We hang the reference electrode in the water and connect the meter to your bonding system, with shore power connected and then disconnected. A fiberglass inboard boat should read between -750mV and -1100mV; the other boat types are in the table below. A reading outside the range is a problem.

Bonding Audit

We physically inspect the green bonding wires in the bilge. We look for green corrosion on terminals and loose connections on thru-hulls and rudders.

Anode Analysis

Are your zincs disappearing too fast? Or not at all (passivated)? We determine if you need more surface area or a different material (Aluminum vs. Zinc vs. Magnesium).

Shore Isolation

We verify your Galvanic Isolator is functioning. This device blocks low-voltage DC current from your neighbor's boat from traveling up your shore power cord and eating your zincs.

Save Your Metals.

Prevention is cheaper than new props.

Marine technician using a Fluke multimeter and Ag/AgCl silver chloride reference electrode to test hull potential and zinc anode efficiency.

Close-up inspection of a corrosion-free marine bonding wire connected to a bronze seacock thru-hull fitting with proper crimping and heat shrink.

Marine technician installing a new sacrificial zinc anode on a boat transom to prevent galvanic corrosion and electrolysis damage.

Target Voltages.

What the numbers mean (vs Ag/AgCl).

Fiberglass (Inboard) -750mV to -1100mV

Aluminum Hull -950mV to -1150mV

Stern Drive (IO) -950mV to -1100mV

Common Questions

My zincs last forever. Is that good?

Usually not. If your zincs are not wearing at all, they are probably not working. They may be "passivated" (coated in a hard shell) or disconnected from the bonding system, and then your prop and other metals can corrode instead.

Should I switch to Aluminum Anodes?

In many cases, yes. Modern Aluminum anodes (Navalloy) last longer and work better in brackish water than traditional Zinc. We can test to see which is best for your marina.

Stop the Rot.

Book a corrosion test today.

Test My Boat

When to Book Electrolysis Testing

Marine electrolysis rarely announces itself. The usual clues are zincs that disappear far too fast, zincs that never seem to wear at all, or pitting on a prop or drive. Any of these is a good reason to book electrolysis testing before the damage spreads to more expensive metal.

The marine electrolysis tester we rely on is a silver-silver chloride (Ag/AgCl) reference electrode placed in the water and connected to your bonding system. It reads the voltage of your underwater metals against the seawater, which shows whether the boat is under-protected, over-protected or in the safe range. From there we check bonding continuity, the condition of your anodes and the galvanic isolator on your shore power. It helps to tell us when your zincs were last replaced and which anode material they are.

Electrolysis testing is a critical step in diagnosing and preventing marine corrosion on your boat's hull, propeller, and other underwater components. This non-invasive process detects the presence of electrolysis, which can cause costly damage through galvanic corrosion. A thorough electrolysis test helps identify potential issues before they become major problems, ensuring you stay afloat with a reliable vessel.

Electrolysis Testing: FAQ

What is the purpose of an electrolysis testing procedure?

This diagnostic service identifies areas where electrolysis may be occurring between dissimilar metals on your boat's hull and underwater components. It helps prevent costly repairs by pinpointing potential corrosion hotspots before they cause significant damage.

How does the bonding system check relate to electrolysis testing?

The bonding system is a critical component in preventing electrolysis, as it ensures all metal parts are electrically connected to prevent stray current corrosion. Our technicians inspect and test this system to ensure it's functioning correctly and recommend repairs or upgrades if necessary.