Australian pontoons combine aluminium, stainless steel, galvanised steel, electrical systems and boats with their own bonding systems. Poor interfaces can destroy expensive structures.
Buyer checks
- aluminium alloy and temper
- stainless grade
- isolation washers/sleeves
- coatings on steel piles
- sacrificial-anode strategy where applicable
- copper-containing products near aluminium
- shore-power leakage monitoring
- drainage and crevice details
- corrosion allowance
Used pontoon clue
White powdery aluminium corrosion, deep pitting around stainless bolts, bubbling coatings, rust bleeding from steel reinforcement and recurring anode consumption deserve investigation rather than cosmetic cleaning.
Corrosion is a design decision, not a maintenance problem
Most corrosion damage on Australian pontoons is designed in, not worn in. Dissimilar metals are put in contact, water is allowed to sit in a detail that cannot drain, or a fitting is specified in a material that loses to the one it is bolted to. Maintenance then spends years managing a problem that a drawing created.
The diagram above shows why: couple two metals in seawater and the less noble one gives up material to protect the other. Every stainless fitting on an aluminium structure is one half of that couple.
Questions to settle before you specify
- Which metals are in contact anywhere in the structure, and what isolates them?
- Where can water sit, and how does every closed detail drain?
- What anodes are fitted, where, and what do they protect?
- Is there any stray-current source nearby — shore power, a neighbouring vessel, cathodic protection on another structure?
- What coatings are used, and what maintenance do they assume?
What to put in the RFQ
- Materials schedule covering structure, fasteners and fittings.
- Isolation method at every dissimilar-metal junction.
- Anode type, mass, location and expected replacement interval.
- Drainage detail for closed sections.
- Coating system and its maintenance regime.
Where corrosion management fails
- Stainless fasteners into aluminium with no isolating washer or sleeve.
- Closed sections with no drain path, holding salt water permanently.
- Anodes fitted but never inspected or replaced.
- Crevices formed where two surfaces are clamped together and never dry.
- Stray current from a nearby installation, never investigated.
Questions buyers ask
Are anodes a consumable?
Yes. They work by being consumed, which means they have a replacement interval and belong on the maintenance schedule with a record of when they were changed.
Is aluminium a bad choice in salt water?
Not inherently — much of the Australian market is aluminium. What matters is alloy selection, detailing, isolation from other metals, drainage and an anode strategy that is actually maintained.