Shipbuilding & Marine

Seawater is the harshest natural electrolyte: roughly 19,000 ppm chloride 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 & Material Selection

Part	Grade	Surface / Size	Watch Out For
Deck Railings / Fittings	316L	Tube / Section, Polished	Salt-spray corrosion, post-weld passivation
Seawater Piping	2205 / 6Mo	Seamless / Welded Tube	Pitting, erosion-corrosion
LNG Tank Inner Shell	304L / 304	Plate 8–50 mm	Low-temperature toughness, classification approval
Accommodation / Galley Fittings	304 / 316L	8–2 mm, 2B/HL	Cleanability, fingerprint resistance
Fasteners / Mounting	316 / 2205	Rod / Forgings	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 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 support-to-hull contact points, 304 shows rust within months. Design crevices out (continuous welds, drain holes) and upgrade to 316L or 2205.

Confirm Class Approval Early

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

Welding Distortion Accumulates in Assembly

Thin fitting parts warp and errors stack up at final assembly. Pre-fabricate as sub-sections using anti-distortion fixtures and leave allowance for trimming.