304 vs 316 vs 631 stainless spring wire.

304 vs 316 vs 631 stainless spring wire

Same shiny finish. Very different performance.
Specifying the wrong one doesn't just affect cost —it affects whether your spring survives the application at all.

Here's the plain-English breakdown:

304 Stainless — The default choice
Most common. Most affordable.
Works well for indoor, dry, low-corrosion environments.

Where it fails:
→ Saltwater or high-humidity exposure
→ Contact with chlorides (cleaning agents, sweat, seawater)
→ Sustained high-temperature applications above 150°C

If your product lives indoors and doesn't touch chemicals — 304 is usually fine.

316 Stainless — The corrosion-resistant upgrade

Contains molybdenum, which dramatically improves resistance to chloride corrosion.

Best for:
→ Marine and outdoor environments
→ Food processing and medical equipment
→ Any application involving cleaning chemicals or moisture

Cost is roughly 20–30% higher than 304. Worth every cent in the right application.

631 (17-7PH) — The high-performance option

Precipitation-hardened stainless. Higher tensile strength,better fatigue resistance, retains performance at elevated temps.

Best for:
→ Aerospace and precision instruments
→ High-cycle fatigue applications
→ Operating temperatures up to 300°C

Significantly higher cost. Only specify it when 316 isn't enough.

That's it.