Compare 304 vs 316 stainless steel hex bolts for your project. Learn corrosion resistance, strength, pricing, and factory supply options. Expert guide from TradeGo fasteners.
304 vs 316 Stainless Steel: Key Differences
Stainless steel hex bolts are essential for applications requiring corrosion resistance. Type 304 contains 18-20% chromium and 8-10.5% nickel, making it ideal for general indoor and outdoor applications. Type 316 adds 2-3% molybdenum, dramatically improving resistance to chlorides and marine environments. For construction fasteners in coastal areas or near saltwater, 316 is the clear choice despite its 20-30% higher cost. Both grades are non-magnetic in annealed condition and meet ASTM F593 (316) and ASTM A193 Grade B8 (304) specifications. When selecting between grades, consider the service environment: inland industrial applications typically suit 304, while harbors, chemical plants, and marine installations require 316.
Factory Supply: Full Thread vs Half Thread Hex Bolts
Factory supply of stainless steel hex bolts includes both full thread and partial thread options. Full thread hex bolts (DIN 933 / ISO 4017) provide maximum clamping force along the entire shank, ideal for applications where the bolt passes completely through the material. Half thread hex bolts (DIN 931 / ISO 4014) offer higher shear strength at the unthreaded shank and are preferred for structural connections where the thread does not extend into the shear plane. Long hex bolts (also called tap bolts) with extended shank lengths are available for specialized applications requiring extra engagement. Our factory stocks M6 to M30 sizes in both 304 and 316 grades, with A2-70 and A4-80 strength classifications available.
Marine Grade 316 Hex Bolts for Ship Building
The marine industry demands fasteners that withstand constant saltwater exposure. Grade 316 stainless steel hex bolts provide superior corrosion resistance in these harsh conditions. Ship building applications include deck fittings, hull connections, railing systems, and engine mounting where both strength and corrosion resistance are critical. Our marine grade bolts meet ASTM A193 B8M requirements and are tested for resistance to pitting and crevice corrosion in simulated seawater environments. The molybdenum content in 316 specifically protects against chloride ion attack, which is why classification societies require 316 or higher for above-water hardware on vessels operating in tropical waters.
304 vs 316 Stainless Steel Hex Bolt Specifications
Compare mechanical properties and chemical composition of 304 and 316 stainless steel hex bolts for accurate specification selection.
| Property | 304 Stainless | 316 Stainless |
|---|---|---|
| Chromium Content | 18-20% | 16-18% |
| Nickel Content | 8-10.5% | 10-14% |
| Molybdenum Content | None | 2-3% |
| Tensile Strength | 515 MPa min | 515 MPa min |
| Yield Strength | 205 MPa min | 205 MPa min |
| Corrosion Resistance | Good (indoor/outdoor) | Excellent (marine) |
| Chloride Resistance | Limited | Excellent |
| Price Premium vs 304 | Baseline | +20-30% |
| Common Standards | DIN 933, ASTM F593 | DIN 933, ASTM A193 B8M |
Frequently Asked Questions
What is the price difference between 304 and 316 hex bolts?
316 stainless steel hex bolts typically cost 20-30% more than 304 grade. The premium is due to molybdenum content and superior corrosion resistance.
Can 304 stainless steel bolts be used outdoors?
304 bolts work outdoors in dry, non-coastal environments. For coastal, marine, or high-chloride environments, always use 316 or higher grade.
What does A2-70 and A4-80 mean?
A2-70 is the designation for 304 stainless steel with minimum tensile strength of 700 MPa. A4-80 is 316 stainless steel with 800 MPa minimum tensile strength.
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