How to Inspect Sailboat Chainplates for Leaks, Cracks and Hidden Corrosion

Count the chainplates on each side and at the bow and stern, and photograph each one on deck. Note the type (through-deck, external on the hull, or glassed in). This list is what you'll compare each year.

Wipe each chainplate and gently scrub any rust with a gray nylon pad. BoatUS stresses that anything more than light rust staining can be a sign of crevice corrosion; you need to see bare metal. Never use steel wool on stainless; it leaves particles that rust.

Look closely, especially at the edges and around the pin hole:

• Hairline cracks, particularly just above the deck and around the clevis pin hole
• Pitting or rust "blooms" along the edges
• A clevis pin hole that has stretched into an oval
• A chainplate that is bent or not lined up with its shroud (Practical Sailor lists bad lead angle as a warning sign)
• Missing or worn cotter pins in the turnbuckle and toggle

Photograph anything suspicious with the camera in close-up mode, then enlarge it later on a bigger screen.

Look at the sealant or cover plate where the chainplate goes through the deck. BoatUS says it should not be cracked, peeling or pulled away. Gaps, dark staining and dried-out sealant all mean water is getting in.

Tap around each chainplate with a plastic mallet and compare the sound with deck farther away. A dull thud, flexing or gelcoat cracks around the chainplate point to wet or rotten core. See /guides/deck-core-moisture.

Remove trim panels or liners to see where each chainplate bolts on below. Look for:

• Water stains, dark wood, soft or delaminated plywood on the bulkhead
• Rust streaks running down from the chainplate
• Cracks or rust at the edges of the plate and around its bolts
• Bolts that look loose or nuts that are rusted

A rotten bulkhead can let go and release the chainplate even if the metal is sound. BoatUS treats this as just as serious as a cracked plate.

BoatUS warns that painting chainplates hides corrosion; by the time rust shows through the paint, the plate needs replacing. If yours are painted, look extra hard at any bubbling or rust spots and ask a rigger to check them.

If a chainplate is fully glassed into the hull or a bulkhead, you can't see it. Don Casey (SAIL) explains that a leak can leave its base sitting in stagnant water, which is exactly when corrosion starts. X-ray and ultrasonic testing exist but are costly and not certain. His advice is that the reliable fix is to open up the encapsulation, inspect, and attach new or existing plates in a way that can be seen in future. Plan this with a rigger or surveyor.

Small leaks at the deck can often be fixed by resealing the deck opening without removing the chainplate, but the rig must be safe:

• Ask a rigger first if you are unsure. Only work on one chainplate at a time, with the mast supported by a halyard or temporary stay led to a strong point if you must slack its shroud.
• Remove the cover plate (if any), dig out the old sealant completely, clean with the sealant maker's solvent and let it dry.
• If the hole is open to wet core, the core needs sealing first (see /guides/deck-hardware-rebedding for the epoxy fill method).
• Rebed with a flexible sealant meant for hardware that moves. Owners and riggers commonly use butyl tape or polysulfide; avoid silicone, which doesn't keep water out long term and leaves residue new sealant won't stick to. Check what your rigger or the sealant maker recommends.
• Water-test with a hose afterward.

Chainplates should come out for a full inspection (and possibly polishing, dye testing or replacement) when:

• You find any crack, deep pitting, or more than light rust staining at the deck or below
• The bulkhead or knee is wet, stained or soft
• The boat is older and the chainplates have never been pulled. BoatUS's rigging author, marine surveyor Dylan Bailey, says that if you want to be sure, he would replace them after about 20 years of service, or sooner if there is any crevice corrosion, which can appear in under 15 years in harsh conditions.
• You are about to replace the standing rigging or head offshore

There is no single "replace by" age. Experts differ:

• Replace on age: Bailey (BoatUS) leans toward new plates at about 20 years. A Cruising World article quotes surveyor Ross Hubbard: on older boats he prefers pulling the plates completely and inspecting them under strong magnification with dye penetrant, rather than just looking at them in place, and any sign of leaking above or below deck means they should come out.
• Replace on condition: The Rigging Company, a rigging shop based in Annapolis, says to replace chainplates when there is damage or cracking, and to replace all of them if one shows wear (unless the damage clearly came from an impact). It lists extreme age, around 30 years or more depending on region and use, as only one factor, along with heavy miles such as a circumnavigation. It also suggests lifting, cleaning and resealing the deck cover plates every two to three years, give or take.
• What both views agree on: leaks are the real enemy. In the same Cruising World article, a rigger said most of the chainplates he inspects need replacing, mostly because of water getting in. Let your rigger or surveyor make the call for your boat.

Pulling chainplates means taking load off the mast. Have a rigger do it, usually with the mast unstepped or properly supported (see /guides/mast-stepping-unstepping).

Chainplates are part of the whole standing rigging system. Do the swage, wire and turnbuckle checks in /guides/sailboat-rigging-inspection at the same time.

Save your photos and notes in your BoatMend log, labeled by chainplate. Next season, compare side by side. Growing rust, new stains below or a sealant line that keeps cracking all tell you to schedule a rigger.