Building materials for seasteads
The high seas are (theoretically) open and free, but come with many construction challenges. Waves and winds should be familiar to all of us. I'm going to talk about construction materials options in the presence of the unholy trinity of biofouling, chloride corrosion, and UV.
Aluminium. Lightweight, inexpensive, easily recycled, handles UV well. Moderate difficulty to work and to repair. No particular resistance to biofouling if left in contact with water, but is not vulnerable to burrowing. Is destroyed very quickly by chloride corrosion. Not a practical option unless you are in a low-chloride environment like the Great Lakes of North America.
Cupronickel (including gunmetal, admiralty brass and similar). Moderately easily worked and recycled. Heavy. Invulnerable to UV. Extreme resistance to biofouling (toxic to invertebrates but not mammals or plants). Decent strength in tension compression and shear. Decent creep resistance. Horribly expensive. Resistant but not immune to chloride attack - no crevice corrosion or pitting, but sheds material very slowly across its entire surface. Combined with its cost this is like watching banknotes blow over the side. Can be practical for piping and similar when too small or inaccessible for inspection and maintainence.
Polymers (plastics). Lightweight, inexpensive. Uniquely vulnerable to UV, this can be managed with coatings, free-radical stabilisers and UV-absorbent fillers such as titanium dioxide. Mostly low strength, lower stiffness and no creep resistance unless reinforced with glass fibre, carbon fibre, or metal fibre. Easily recycled... unless you add fillers or reinforcement: you need both. Good resistance to biofouling. Essentially immune to chloride attack (though metal fittings and reinforcement might be vulnerable). Cheap and practical to build, moderately easy to repair, impossible to recycle.
Steel, coated. Very easily worked and repaired, moderately easily recycled. Cheap. Moderately heavy. Immune to UV. Coating can provide good resistance to biofouling. Excellent strength in tension, compression and shear. Excellent creep resistance. Quite vulnerable to chloride corrosion and related sulphate corrosion, can be managed with constant inspection and maintainance. Best option for working boats / infrastructure that expect to be damaged and repaired almost constantly.
Steel, stainless 316. Easily worked and repaired, moderately easily recycled. Expensive. Moderately heavy. Immune to UV, highly resistant to biofouling, more so if coated. Excellent strength in tension, compression and shear. Excellent creep resistance. Resistant to chloride and sulphate corrosion, doubly so if coated. This is not true of the cheaper 304 stainless and similar. Best all-rounder if you can afford it.
Your thoughts? Other options I may have overlooked?
