Hex Bolts, “Marine Quality” Type 316 Stainless Steel

“Marine Quality” Stainless Steel Hex Bolts are sold in various lengths and diameters and are made from 316 Grade Stainless Steel. Hex bolts are sold in full box quantities. *Box quantities may vary.

A 316 marine-quality hex bolt offers significantly better corrosion resistance than a 304 stainless bolt when used in saltwater or chloride-rich environments, making it the preferred choice for marine hardware, offshore structures, and coastal installations.

Key differences and benefits:

• Molybdenum content: 316 contains 2–3% molybdenum, which 304 lacks. Molybdenum stabilizes the chromium oxide passive layer, making it far more resistant to chloride-induced pitting and crevice corrosion
• Pitting resistance: In seawater, 316 can last 3–5 times longer than 304 before significant pitting occurs. 304 may fail in 3–5 years in moderate marine conditions, while 316 can withstand 10–15 years before visible corrosion
• Crevice corrosion resistance: Both grades are vulnerable in tight spaces (e.g., under washers, in threads), but 316’s molybdenum content reduces the risk of localized corrosion in splash zones and tidal areas
• Service life in marine environments: Because of its superior chloride resistance, a 316 bolt maintains load capacity and structural integrity far longer in salt spray, tidal splash, or submerged conditions
• Galvanic corrosion mitigation: In galvanic pairs (e.g., with aluminum), 316’s corrosion resistance helps reduce the rate of degradation compared to 304

When to choose 316 over 304:

• Any application exposed to seawater, salt spray, or high-chloride environments.
• Underwater installations, offshore platforms, marine vessels, or coastal infrastructure.
• Where long-term reliability and minimal maintenance are critical.

When 304 may still be acceptable:

• Dry, non-chloride environments.
• Short-term or low-exposure projects where cost is a primary concern.

Bottom line:
For marine-quality hex bolts, 316’s molybdenum content provides a critical performance advantage in resisting pitting and crevice corrosion, extending service life and reducing failure risk in harsh chloride environments