53368

416 SS, Images and data for salt spray testing (fog) [Connecticut] 

October 16, 2009

Hello:

I sell industrial hdwe & fastener in So New England.

I get frequent questions from engineers designing new and upgraded products for outdoor application most often requiring SS or aluminum products mixed in the application.

This poses several issues to the ocean atmosphere here in New England.

This current customer request is all SS construction.

My customer is upgrading an exterior metal product with a spring loaded screw machine part.

The mfr is calling out a 416 SS w/ Blk Nitride finish(for appearance)for this part and as the product is installed along the coast line my customer has been opting for 300 series SS construction for all the other parts for their product upgrade.

The concern is about the longevity of the part in the ocean atmosphere as it can not display "rust"/ corrosion for several years and has a product life of 20 years.

As these are small parts on a larger unit mounted up on a post (8-12" high they will not get frequent inspection but on the occasion of maintenance to the unit they need to appear presentably and work freely when turned.

The customer is asking for both performance ratings/results and an image of the material after salt testing to show what the discoloration can look like.

Can I get help in resources for this data.

Thank you

Ivan Leibin
Industrial Hardware Sales - West Hartford, CT, USA

For decorative SS items (handrails and sculptures, mostly) placed along oceanfronts, we always recommended 316 or better, and in that environment even the 316 generally needs annual or semiannual treatment to clean up "tea staining" corrosion and repassivate the surface.

Since your object is a functional part it may be hard to change to a different alloy as that could affect the mechanical properties. However you may have no choice if you need years without corrosion.

The black nitride finish may provide some additional corrosion protection.

Ray Kremer Stellar Solutions, Inc. McHenry, Illinois

There's no way I'd use 416 in a marine or salt water environment, and I'd doubt the black nitride will help much if at all. 416 is a free machining, low-chromium martensitic (sometimes) stainless steel. Ease of machining and potential to harden to about HRC 35-40 are it's strong points, but corrosion resistance is one of the weak points.

Lee Gearhart metallurgist East Aurora, NY