Shipbuilding & Offshore

Seawater is the harshest natural electrolyte: about 19,000 ppm chloride plus wet-dry cycling 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 / section, polished	Salt spray, post-weld passivation
Seawater piping	2205 / 6Mo	Seamless / welded tube	Pitting, flow erosion
LNG tank inner shell	304L / 304	Plate 8–50 mm	Low-temperature toughness, class approval
Accommodation / galley equipment	304 / 316L	0.8–2 mm, 2B/HL	Cleanability, fingerprint resistance
Fasteners / securing	316 / 2205	Bar / forging	Stress corrosion cracking

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

Three real constraints in this industry

Crevice corrosion is the dominant failure

Under gaskets and at bracket-to-hull contacts, 304 shows rust within months. Design the crevice out (continuous welds, drain holes) and upgrade to 316L or 2205.

Confirm class approval early

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

Weld distortion accumulates into assembly

Thin outfitting parts distort and the error accumulates at final assembly. Pre-fabricate in sections with anti-distortion jigs and leave trimming allowance.