Performance of Stainless Steel in Marine Environments

Stainless steel | Monday, 09 January 2017

The demand for marine applications has never been greater. As people continue to discover new ways to survive and operate underwater, it becomes essential to look for materials that can provide the best resistance and performance beneath the ocean surface. Although there are quite a few number of materials that are in contention for being labelled as the perfect marine application material, there is very little doubt among experts about the fact that stainless steel overshadows every other object when it comes to underwater applications.

Why Stainless Steel is Used in Marine Applications

One of the main reasons why the use of stainless steel is such a necessity for the completion of marine applications is the unparallel resistance to corrosion or rust that it provides. No other material can shield itself from rust like stainless steel does. Since objects underwater are exposed constantly to moisture and oxygen, the formation of rust or the act of corrosion becomes quite inevitable if the submerged object is made of any kind of metal. An argument can be made for bronze, brass and galvanized steel which were used in the construction of ships before the discovery of stainless steel. However, none of these materials are nearly half as impressive as stainless steel when it comes to keeping the rust away and maintaining the top notch condition of the submerged objects or media of transport.

Stainless Steel Is Not Immune to Underwater Corrosion

With that being said, it has recently been noticed that stainless steel, despite its stand out features, is not completely immune to corrosion when used in marine applications. Crevice corrosion and pitting is bound to develop on stainless steel materials sooner or later if it stays in contact with water. After about a year and a half of service, duplex stainless steel used in marine vessels showed signs of succumbing to corrosion.

Seawater is Naturally More Corrosive

Stainless steel is able to avert corrosion due to the layer of passive chromium oxide that covers its surface. However, when exposed to seawater, another layer is formed above the chromium oxide blanket. This layer, known as a biofilm, affects metal surfaces that are immersed in natural seawater and increases the ability of the water to corrode metal surfaces including stainless steel. As a result, although the corrosion resistance of the stainless steel does not decline, but the increased corrosivity of the seawater causes the stainless steel to corrode eventually.

Types of Corrosion in a Marine Environment

When corrosion takes place in stainless steel materials that are placed underwater, the rust never appears uniformly. In other words, uniform corrosion is not a feature of stainless steel in a marine environment. The corrosion takes place in a localized manner and is often promoted by the layer of biofilm that develops on top of the chromium oxide layer. Since the corrosion is localised, crevice corrosion is a common occurrence in stainless steels that exist in a marine environment. In addition to crevice corrosion, marine stainless steel applications may be subject to stress corrosion cracking and galvanic corrosion.

Despite the handful of shortcomings that stainless steel may have in a marine environment, it goes without saying that it is still the most preferred material in the industry and one that offers the greatest durability and endurance underwater.

Cougartron ProPlus for Stainless Steels

Talking of stainless steel, did you know that the Cougartron Pro Plus is perfect for stainless steel maintenance? The ProPlus is designed to give you the most efficient, the fastest and the safest stainless steel maintenance in the world. Whether it be cleaning, polishing or etching, Cougarton ProPlus is the ultimate device that provides you with a top notch service. It’s easy to use, lasts for a long time and is far more effective than any other system out there. Not to mention, its intelligent electronics allows it to provide consistent power and uninterrupted production.