June 2017

AISI 316L stainless steel pressfittings in environments with salinity - marine aerosol

Plumbing systems in areas with moderate salinity? Eurotubi pressfittings in AISI 316L stainless steel are able to offer excellent resistance to this type of corrosion thanks to the excellent characteristics of 316L stainless steel. Let’s discover these winning characteristics together.

Important information:

Eurotubi pressfittings in AISI 316L stainless steel can be used in environments with moderate salinity. They cannot be used to transport saltwater (and sea water). Cupronickel pressfittings must be used for this application.

For applications in the naval sector, Eurotubi pressfittings are certified according to R.I.N.A. and ABS (American Bureau of Shipping) standards.

For more information, contact the Eurotubi Technical Office.

Steels like 316L are called “stainless” because in oxidizing atmospheres (air and water), they form a protective layer on the surface through a phenomenon called “self passivation".

What is saline corrosion

Corrosion that occurs on metal alloys caused by the presence of chlorine ions is called “pitting corrosion”. It is a type of corrosive attack that develops on an increasing number of points rather than with growth in the individual areas attacked.

Corrosione salina su acciaio inox

The corrosion created by marine aerosol is accentuated in areas jutting into the sea by continuous wetting that the steel may be exposed to. In fact, the presence of chlorine ions is not enough to trigger pitting.

Which elements make 316 and 316L so resistant to corrosion?

The molybdenum contained in AISI 316 and AISI 316L stainless steel increases the resistance of the material to electrolytic corrosion from chlorides (increasing the stability of the passive layer). This makes these two steels particularly effective in environments with the presence of solutions containing chlorine ions - especially if stagnant - like those areas near the sea (and therefore also in naval applications).

tabella con Differenza tra acciaio 316 e 316L nel pressfitting

Content of AISI 316L and 316 steels compared - click on the image to zoom in

Nickel promotes the resistance to crevice corrosion that is typical of environments near the sea and also gives the material excellent ductility and resistance.

Other elements, like phosphorous, nitrogen, silicon, tend to harmonize the entire compound.

Why is 316L potentially better against corrosion than 316?

316L differs from 316 due to its reduced carbon content, so the chrome present in the alloy has less possibility of combining with the carbon and forming chromium carbides. The free chrome, in other words chrome not combined with carbon, creates the passivating oxide layer, which provides protection against corrosion.

Tubi per pressfitting in acciaio inox 316l

The AISI 316L stainless steel used in Eurotubi pressfittings is not completely resistant, but is one of the more resistant steels to saline aerosol. It you are looking for complete compatibility with the passage of sea water, choose the CuNiFe pressfitting.

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