Stainless Steel Corrosion Resistance in Seawater

Corrosion resistance. This post deals with current and possible uses of high-alloy stainless steels in various marine environments for different applications. A survey of the general behavior of stainless steels in seawater.

Localised corrosion in seawater.

Stainless steels such as 316 L or 304 present a poor corrosion resistance in seawater. Stainless steels exposed to seawater may suffer from localised corrosion such as pitting. Often, determined by the presence of interstices.

These can be:

inherent to the project of the component (for example: flanges or seals)
caused over time by the growth of marine organisms and defects or deposits on metal surfaces.

Corrosion resistance in current seawater.

On the contrary, in current seawater with speed greater than about 1 m/s, the tendency to pitting decreases. In fact, at high speeds (to 40 m/s) the steel is free to attacks. In the interstitial zones, the speed will always be equal to zero. However, these may also be subject to corrosion. (whatever the speed value in the outside of interstice)

Where to use stainless steel?

Then, the stainless steels are extremely resistant at high flux speed. This fact increased the use of such materials for components such as: impellers, pump casings, valve parts and mechanisms for the effluent of brine desalination plants or in different applications cases where there are high speed. Where the copper based alloys can fail due to corrosion.