Stainless steel rebar for coastal and bridge construction is most often a choice between 2304 lean duplex and 316LN austenitic. This guide explains the corrosion and cost trade-offs, with selection guidance for marine substructures, bridge decks and critical infrastructure.
Stainless steel rebar is the long-life alternative to coated or galvanized rebar in the most corrosive reinforced concrete environments. The two grades that dominate specification are 2304 (1.4362), a lean duplex stainless, and 316LN (1.4429), a low-carbon austenitic stainless with 2–3% molybdenum. Both are accepted by EN 10088 and ASTM A955 for concrete reinforcement, and both eliminate the corrosion-induced concrete spalling that limits the life of carbon steel rebar in coastal and de-icing salt exposure.
Why Stainless Rebar Instead of Coated or Galvanized
Epoxy-coated, galvanized and stainless-clad rebar all extend the life of reinforced concrete in corrosive environments, but only stainless steel rebar provides a service life that exceeds 75–100 years without protective coating deterioration. Once a coated rebar is cut, bent or damaged during placement, the exposed carbon steel core corrodes at the same rate as uncoated rebar. Stainless rebar has the same composition throughout the bar, so cut ends, bends and minor surface damage do not create corrosion initiation sites.
2304 Lean Duplex: The Right Specification for Most Coastal Projects
2304 lean duplex stainless rebar has about 23% chromium, 4% nickel, 0.1% nitrogen and no molybdenum, giving a PREN (pitting resistance equivalent) of about 25. The strength is roughly twice that of standard carbon rebar (minimum yield 450 MPa for 2304 vs 500 MPa for B500B, but with significant work hardening). For most coastal bridges, piers, seawalls, and parking structures, 2304 gives sufficient corrosion resistance at significantly lower cost than 316LN. It has become the default specification for transportation authority bridge projects in chloride exposure.
316LN Austenitic: The Necessary Upgrade for Severe Exposure
316LN austenitic stainless rebar contains 16–18% chromium, 10–14% nickel, 2–3% molybdenum, and low carbon (max 0.030%), giving a PREN of about 26–28 and excellent resistance to pitting and crevice corrosion in severe chloride exposure. For marine structures in warm seawater, chemical plant foundations where acids may be present, and structures designed for 100+ year service life, 316LN is the conservative specification. The trade-off is significantly higher cost (typically 4–6 times the price of 2304) and a more demanding weld procedure if the bars are to be welded.
Bending, Welding and Coupler Compatibility
Both 2304 and 316LN can be bent to standard rebar bend radii using conventional bending equipment, with no special tooling required. Welding is more demanding: 2304 requires careful control of heat input and interpass temperature to avoid sigma-phase formation, and 316LN requires low-carbon welding consumables to avoid sensitization. For most projects, mechanical couplers and lap splices are preferred over welding. The couplers must also be stainless steel of the same grade to avoid galvanic corrosion at the connection.
What to Specify on the Stainless Rebar RFQ
State the standard (ASTM A955 or EN 10088), the grade (2304 / 1.4362 or 316LN / 1.4429), the nominal diameter (typically 12, 16, 20, 25, 32 mm), the bar length, the bend shape (if pre-bent), and any supplementary requirements (Charpy impact, PREN test report per ASTM A955 supplementary requirement). For most coastal bridges and marine substructures, default to 2304; for severe chloride or acid exposure, default to 316LN. Always confirm the mill supplies a test report per EN 10204 3.1 showing the actual PREN and chemistry, since substitution with a lower-grade stainless is a common quality issue.
Related Resources from Baobin Steel
- Stainless steel bar catalog – 2304, 316LN and other grades
- Stainless steel overview – grade families and standards
- Request a quote – send your rebar schedule for stainless rebar pricing