Corrosion is a maintenance problem, not a material problem
The aluminium hulls that fail early almost never fail because of the alloy. They fail because of a stainless bolt, a wet locker, or a bilge that nobody looked inside for two years.
We get a hull back for repair every few months, and the owner usually says the same thing: it is the aluminium, it corrodes. It almost never is. Aluminium in seawater is a stable material. What fails is the detail around it.
1. Galvanic contact
Put stainless steel in direct contact with aluminium in salt water and you have built a battery. The aluminium becomes the anode and dissolves, quietly, under the fitting. The fix is simple and cheap: nylon or Teflon washers, a bed of sealant, and no stainless fastener touching bare aluminium anywhere on the boat.
Check the stainless cleats, the ladder brackets, the rod holders and the engine mounting bolts. If a fastener has white powder around it, the contact is live.
2. Trapped water
Aluminium needs oxygen to keep its oxide layer intact. Water that sits in a locker, under a floor panel or in a bilge with no airflow creates the one condition where aluminium pits: oxygen starvation. A wet life jacket locker will pit the plate under it in a season.
All our hulls have drain paths from every compartment for this reason, and we will show you where they are when you take delivery. If you add a locker or a fish box after the fact, add a drain with it.
3. Dead anodes
Anodes are the part you replace so the hull does not have to. On a moored boat they should be checked monthly and replaced at 50% loss — not when they are gone. In the Gulf's warm water they corrode faster than the northern-hemisphere guidance suggests, sometimes twice as fast.
Carry spares. An anode is a few dollars; a pitted hull is a welding job and a haul-out.
4. Damaged paint
Paint is a barrier, not a finish. A scratch that reaches bare metal will start to pit within weeks in salt water, and it will grow under the paint edge where you cannot see it. Touch up bare metal with an etch primer and a topcoat within a week, not at the end of the season.
The one-afternoon inspection
- Walk the deck looking for white powder around every stainless fitting.
- Open every locker and look for standing water.
- Look at the anodes — all of them, including the ones on the bracket.
- Run a hand along the keel and chines for paint damage.
- Look in the bilge with a torch, not a glance.
An hour of this once a quarter is the whole difference between a hull that lasts thirty years and one that needs plate replaced at eight. Our care guide has the full schedule, and the patrol hulls we build for crews who work in salt water every day are designed around it.
