Shipbuilding and Offshore

Seawater is the most aggressive natural electrolyte: roughly 19,000 ppm of chlorides, plus wet-dry cycles and crevices. Here the first criterion is not strength — it is whether the material survives crevice corrosion.

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Typical parts and material selection

Part	Grade	Surface / size	Watch out for
Deck railing / outfitting	316L	Tube / profile, polished	Salt mist, post-weld passivation
Seawater piping	2205 / 6Mo	Seamless / welded tube	Pitting corrosion, flow erosion
LNG tank inner shell	304L / 304	Plate 8–50 mm	Low-temperature toughness, class approval
Galley / catering equipment	304 / 316L	0.8–2 mm, 2B/HL	Ease of cleaning, fingerprint resistance
Fasteners / fixings	316 / 2205	Bar / forging	Stress corrosion cracking

These are the usual configurations.Actual selection depends on medium, temperature and welding method— the same component can move from 304 to 316L or 2205. Describing the service conditions is more useful than naming a grade.

Three real constraints in this sector

Crevice corrosion is the dominant failure mode

Under gaskets and at bracket-to-hull contacts, 304 shows rust within months. Eliminate the crevice at the design stage (continuous welds, drain holes) and move up to 316L or 2205.

Confirm class approval early

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

Weld distortion accumulates during assembly

Thin outfitting parts warp and the error accumulates in final assembly. Prefabricate in sections with anti-distortion jigs and leave trim allowance.