How to Select SUS304 vs. SUS316 for Marine Use

Key Differences for Marine Environments

Composition: 304 is 18/8 stainless (18% Chromium, 8% Nickel); 316 adds molybdenum (2-3%), boosting corrosion resistance.

Corrosion Resistance: 316 excels in chloride-rich saltwater; 304 struggles and can rust in these conditions.

Cost: 304 is cheaper; 316 costs more due to molybdenum but offers better long-term value in marine settings.

When to Use SUS304

Freshwater: Boats on lakes or rivers, or fittings frequently washed with fresh water.

Interior: Non-exposed areas, galley equipment (not constantly splashed).

When to Use SUS316 (Recommended for Marine)

All Saltwater Exposure: Deck fittings, railings, hardware (cleats, hinges), rigging, anchors, propellers, and any below-deck components near the hull.

Harsh Coastal Areas: Where sea spray and salty air are prevalent.

The Verdict
If it's for a boat or marine structure, always lean towards SUS316 for critical parts to prevent premature failure from saltwater corrosion, even if it costs more upfront. SUS304 will likely require frequent replacement or maintenance in these conditions.