Stainless steel is one of the world’s most versatile and commercially viable materials available to builders today. Since its development more than a century ago, stainless steel has transformed numerous industries thanks to its many benefits, not least of which is its tremendous corrosion resistance, from which the material gets its name. It is thanks to its ability to withstand corrosion that stainless steel is one of the preferred materials for structures in a marine environment.
Most materials, including carbon steel, are quickly rendered unusable when exposed to seawater for an extended period of time. Stainless steel has the advantage of being corrosion resistant and, especially when the right alloys are used, has extended humanity’s ability to work next to, in, and on top of the world’s oceans. One application that frequently makes use of stainless steel is platform accommodation.
What Is Platform Accommodation?
Known as either platform accommodation or an accommodation platform, these structures are offshore platforms that support living quarters for offshore workers and personnel. Accommodation platforms are most often used as part of the Oil and Gas industry, which relies on offshore platforms for resource extraction. Other industries include wind energy and scientific research.
For those unfamiliar with platform accommodation, these structures are surprisingly large, with the capacity to support dozens or more full time residents. As an example of the scale, the BG Armada Platform Accommodations is currently developing three gas and condensate fields simultaneously in the Central North Sea, 250 km east of Aberdeen, Scotland. The residential facilities on the platform are designed to accommodate 59 personnel.
In addition to being corrosion resistant in a marine environment, platforms must also be structurally stable to bear all necessary heavy equipment, withstand frequent high winds and waves, and maintain its structural integrity in the case of fire or explosion. The required design life of the platform was 30+ years. The structural cladding of the BG Armada modules was made up of corrugated stainless steel that was austenitic grade 1.4401 (S31600).
Oil and natural gas platforms are found all over the world, and so must be designed for the particular climate and conditions. In addition, there is a great deal of variance between platforms in terms of their design and structure. Stainless steel, because of its versatility and the diversity of alloys, is able to meet all the requirements of platform construction, no matter what the location.
What Makes Stainless Steel Suitable For A Marine Environment?
The first factor that makes stainless steel a desirable material in marine environments can be found in the name itself. Stainless steel was developed specifically with corrosion resistance in mind and has a long history of effectively dealing with exposure to water.
Unlike carbon steel, stainless steel has a significant amount of chromium added to it, which protects it from rusting when exposed to air and moisture. The chromium content helps prevent an iron oxide surface layer from forming thanks to a process known as passivation. Instead, a microscopically thin inert surface film of chromium oxide is generated when it comes into contact with oxygen in the air. This process occurs even in water thanks to the presence of dissolved oxygen.
The chromium oxide layer prevents further corrosion because it blocks oxygen diffusion on the metal’s surface, protecting the core of the material. Furthermore, the outer layer has the ability to heal itself in case it is scratched or is disturbed by the environment. Of course, not every stainless steel alloy is well suited for a marine environment, and so it’s important to select the right grade.
What Alloys Work Best In A Marine Environment?
There are a number of considerations that manufacturers must take into account when selecting a stainless steel for their platform accommodation. First of all, the chloride content of the water has a significant affect on marine structures, and will be one of the most important factors that determine what alloy is best suited.
Additionally, when designing the platform structure, as much as possible avoid crevices, as these are especially susceptible to corrosion. The fabrication methods are also critical, in particular when it comes to weld heat tint. Finally, it’s also important to drain promptly after hydrotesting.
Marine grade stainless alloys most often rely on molybdenum content to withstand the corrosive effects of sodium chloride. The most common alloy for a marine environment is SAE 316 stainless steel, a molybdenum-alloyed steel that offers superior resistance to pitting corrosion. Although 316 is not entirely rust-proof, it offers more corrosion resistance than the other stainless steels that are most common. However, in extremely corrosive environments, specialty stainless steels such as Type 2205 and super austenitic and super duplex varieties are used.
What Other Marine Applications Is Stainless Steel Well Suited For?
Platform accommodations are not the only marine applications that rely on stainless steel. Everything from plumbing and wastewater treatment to desalination and shipping and shipbuilding structures rely on modern stainless steel. The great diversity of specialty grades means that all manner of cutting edge applications have been developed.
Additionally, while not strictly a marine environment, medical equipment and surgical tools are also exposed to corrosive elements including sodium chloride. SAE 316 is commonly employed in food processing, chemical storage and transport, textile dying equipment, cladding of nuclear fuel, oil refining equipment, and medical implants.
Summary
Clinton Aluminum and Stainless Steel is more than just a raw material supplier. We make it our top priority to work with our clients as invested partners. We want to make sure you pick just the right material for every job so that you get the maximum return. Therefore, we consult with our clients at every step of the process, sharing our deep knowledge of industry best practices.
Clinton is the Midwest’s leading supplier of aluminum and stainless steel products, and our continued success rests on our commitment to excellence in service. Contact a member of our knowledgeable staff to discover more about how Clinton Aluminum and Stainless Steel can help you beat out your competition.
Resources: https://www.oilandgasonline.com/doc/bg-armada-platform-accommodations-provided-by-0001
