Shipbuilding & Offshore

Seawater is the most aggressive natural electrolyte: roughly 19,000 ppm chloride, combined with wet-dry cycling and crevices. Here the first criterion is not strength — it is whether the material can resist crevice corrosion.

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Typical Components & Material Selection

Component	Grade	Surface / Size	Key Considerations
Deck Railings / Fittings	316L	Tube / Profile, Polished	Salt spray; post-weld passivation
Seawater Piping	2205 / 6Mo	Seamless / Welded Pipe	Pitting; flow-induced corrosion
Inner Shell of LNG Tanks	304L / 304	8–50 mm Plate	Low-temperature toughness; classification society approval
Accommodation / Galley Equipment	304 / 316L	8–2 mm, 2B/HL	Cleanability; fingerprint resistance
Fasteners / Fixings	316 / 2205	Bar / Forgings	Stress corrosion cracking

These are commonly used configurations.Actual selection depends on the medium, temperature, and welding method.The same component may shift from 304 to 316L or 2205 — describing the service conditions is more useful than specifying a grade.

Three Practical Constraints in This Industry

Crevice corrosion is the dominant failure mode.

Under gaskets and at fastener-to-hull contact points, 304 will rust within a few months. Design out crevices (continuous welds, drain holes) and upgrade to 316L or 2205.

Confirm classification society approval early.

DNV / ABS / LR / CCS each maintain their own approved material lists. A superior grade that is not approved will still fail inspection — verify at the quotation stage.

Weld distortion accumulates through to assembly.

Thin fabricated parts distort and tolerances stack up during final assembly. Pre-fabricate in sub-assemblies with anti-distortion jigs and allowance for trimming.