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Stainless Steel Fastener Selection — Quick Reference (304 vs 316)
Stainless steel fasteners are essential for marine + food + chemical + outdoor + architectural applications where standard zinc-plated/galv fasteners corrode unacceptably. Selection turns on grade (304 general / 316 chloride) + strength (standard vs Bumax high-tensile) + fastener type.
| Stainless Grade | Best For | Tensile Strength |
|---|---|---|
| 304 Stainless (A2) | General corrosion + indoor outdoor — workshop default SS | 500-700 MPa standard |
| 316 Stainless (A4) | Marine + chloride + chemical + saltwater | 500-700 MPa standard |
| Bumax 88 (304-Strength = 8.8) | Combined corrosion + medium strength | 800 MPa — equivalent to Grade 8.8 in stainless |
| Bumax 109 (304-Strength = 10.9) | High-strength corrosion-resistant — premium | 1,040 MPa |
| Bumax 125 (Strongest SS Available) | Aerospace + defence + critical engineering | 1,250 MPa (exceeds Grade 12.9 in SS) |
| Duplex Stainless (2205 / 2507) | Severe chloride + high-strength corrosion | Higher strength than 316 + better chloride resistance |
| 410 / 416 Free-Machining | Self-tapping + machined fasteners — magnetic SS | Lower corrosion than 304/316 |
Critical 304 vs 316: 304 corrodes in chloride (saltwater + coastal + chlorine). Use 316 for any marine + coastal + swimming pool + chemical service. Cost difference 316 vs 304 is ~30%; worth it where required. Both 304 and 316 are NON-MAGNETIC (austenitic). Galvanic corrosion: avoid mixing SS with carbon steel in wet contact — couple anodic mild steel to cathodic SS = mild steel corrodes fast. Brands: Inox World, Bumax, Hobson, Bremick, Champion. Companion: all fasteners, hex bolts + nuts, SHCS.
Stainless Steel Fasteners — 304 and 316 Grade for Australian Industry
Stainless steel fasteners are essential for marine, food processing, chemical, outdoor, and architectural applications where standard zinc-plated or galvanised fasteners corrode unacceptably. AIMS Industrial stocks 200+ stainless fasteners from Inox World, Bumax, Hobson, Bremick, and Champion — covering bolts, nuts, screws, washers, threaded rod, and rivets in both 304 (A2) and 316 (A4) marine grades.
304 vs 316 stainless — which grade?
The grade choice is driven by the corrosive environment, not the load:
- 304 stainless (A2) — the general-purpose stainless. Resists most corrosive environments encountered in food processing, dairy, indoor plumbing, mild outdoor exposure, and architectural use. Cost-effective for most non-marine applications
- 316 stainless (A4) — adds molybdenum for resistance to chloride attack. Required for marine, coastal, swimming pool, and chemical environments where 304 would suffer pitting corrosion. Visually identical to 304 but mechanically marked or supplier-certified
- Bumax (high-strength stainless) — A4-80 and A4-100 grades reach mechanical properties approaching Grade 8.8 carbon steel while retaining stainless corrosion resistance. Used for structural and machine assembly where both strength and corrosion resistance matter
Product range stocked
- Hex bolts and set screws — DIN 931, DIN 933 in M3 to M24 across 304 and 316
- Socket head cap screws — DIN 912 in 304, 316, and Bumax high-strength
- Countersunk and button head screws — ISO 10642, ISO 7380 for low-profile and flush-fit applications
- Self-tapping and self-drilling screws — for sheet metal, decking, and roofing applications
- Hex nuts, nyloc nuts, dome nuts, and flange nuts — DIN 934, DIN 985 across both grades
- Flat washers, spring washers, and Nordlock — sized to match metric and imperial fasteners
- Threaded rod, U-bolts, and eye bolts — for structural and rigging applications
- Rivets and rivet nuts — for sheet metal joining where corrosion resistance is required
Galvanic corrosion — important note
When stainless fasteners pass through carbon steel, aluminium, or galvanised components, galvanic corrosion can attack the less-noble material at the contact point. In wet, salty, or chemical environments, isolate dissimilar metals with insulating washers or use the same material throughout the assembly. The fastener may look fine but the parent material around it can deteriorate rapidly.
Magnetism note
304 and 316 austenitic stainless steels are nominally non-magnetic, but cold-working during fastener manufacture induces some magnetism. Don't use a magnet test to verify stainless grade — it's not reliable. For grade certification (especially food and pharmaceutical applications), request material certificates with the order.
Related products
See also: Inox World stainless range, Bumax high-strength stainless fasteners, and general hex bolts for non-stainless applications.
For volume requirements, custom thread forms, or grade certification, contact our team.