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topic 9357

Stainless Steel Grading Numbers, What are They?


We are a manufacture of traffic cameras for the intelligent transportation industry. We utilize stainless steel bolts, screws, washers for all external (exposed to weather)mounting hardware. Would Type 316 SST or 304 Type SST be more appropriate? What are the differences between 304 and 316 SST?

Many thanks,

Daniel Fancher
Wireless Technology, Inc. - Ventura, California, USA


Hello Daniel!

316 is 304 with about 2% molybdenum added, which gives it pitting resistance in salt atmospheres. Go with the 316. This is a no-brainer.

For a great guide, surf over to the nickel development institute at, and have them send you a copy of their technical publication 9014, on "Design Guidelines for Stainless Steels". It's free, and you'll be glad you did.

Good luck!

lee gearhart
Lee Gearhart



Either grade of stainless will serve your purpose. 316 grade fasteners may be hard to find and certainly more expensive. Just be sure the fasteners are properly passivated, and keep them from coming in contact with carbon steels during assembly.

Dan Weaver
- Toccoa, Georgia

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