Shipbuilding & Marine

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

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Typical parts and material selection

Part	Grade	Finish / Size	Watch out for
Deck railing / outfitting	316L	Tube / profile, polished	Salt spray, post-weld passivation
Seawater piping	2205 / 6Mo	Seamless / welded pipe	Pitting, flow erosion
LNG tank inner shell	304L / 304	Plate 8–50 mm	Low-temperature toughness, class approval
Galley / accommodation fittings	304 / 316L	8–2 mm, 2B/HL	Cleanability, fingerprint resistance
Fasteners / fixings	316 / 2205	Bar / stud	Stress corrosion cracking

These are typical configurations.Actual selection depends on environment, 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 sector

Crevice corrosion is the main failure mode

304 rusts within months under gaskets and where brackets meet the hull. Design the crevice out (continuous welds, drain holes) and move to 316L or 2205.

Confirm class approval early

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

Welding distortion accumulates at assembly

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