Shipbuilding
Structures the size of buildings that have to float in the most corrosive ordinary environment there is.
Building and repairing vessels. Two constraints shape every material decision: seawater, which is a warm aerated chloride solution and attacks almost everything, and scale, which rules out any material that cannot be produced by the thousand tonnes and joined by ordinary welding.
That combination is why ships are made of steel that rusts and is protected, rather than of a metal that does not rust. Stainless steel is vulnerable to exactly the crevice and pitting attack a hull provides, and the economics of a ten-thousand-tonne structure do not admit anything exotic.
History
Timber until the nineteenth century, and the shift to iron and then steel is one of the clearest cases of a material changing what could be built: a wooden hull has a practical length limit set by the timber and the joints, and an iron one does not.
Welded construction replaced riveting during the Second World War in the American Liberty ship programme, which also produced the field's most instructive failure — hulls cracking in cold water because the steel's ductile-to-brittle transition had not been understood, and a welded structure gives a crack an uninterrupted path a riveted one does not.
Economic significance
Around eighty per cent of world trade by volume moves by sea, on ships built in a small number of yards concentrated in East Asia. The industry is a very large consumer of plate steel and of protective coatings.
Its environmental questions are increasingly material ones: antifouling coatings after the ban on tributyltin, ballast water, and the ship recycling that happens on beaches in South Asia and is the end of life for most of the world's steel afloat.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
uses
- Steel — alloy · hulls and superstructure, and the choice is a metal that rusts and is protected rather than one that does not rust — nothing else can be produced and welded at ten thousand tonnes
- 5000 series aluminium alloy — alloy · hulls and superstructures where weight above the waterline matters, and it is chosen over stronger aluminium for its welds
- Epoxy resin — material · hull composites and protective coatings
- Cupronickel — alloy · seawater piping and condenser tubes, where its resistance to biofouling matters as much as its corrosion resistance
- Welding — process · which replaced riveting during the Second World War, and taught the industry about brittle fracture in the process
- Glass fibre composite — material · small craft almost entirely, since a moulded hull needs a mould and unskilled labour where a wooden one needs skill and maintenance
Sources
- Material WorldOur own writing
- Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)