Marine-grade stainless steel is a widely used term in the construction industry because certain types of the alloy have been developed to work particularly well in situations where saltwater and spray may be present. Engineers will often specify the use of marine grades of the metal for installations that will take place at quays or harbours, for example. However, there is no industry-wide definition of what marine-grade stainless steel actually is. In fact, along with types 303 and 304, it is grade 316 stainless steel that is usually chosen when a marine grade of stainless steel is called for. What properties do these types of stainless steel offer that make them good choices?

Chloride Corrosion Resistance

Anywhere where stainless steel will be in close proximity to seawater needs a greater level of chloride corrosion resistance than other metals. Marine grades of stainless steel are much slower to react to the salt in water, and if they are splashed on, the water subsequently evaporates, leaving a salty residue. Anywhere that brackish or still water may be present may require a marine grade of stainless steel. Although pitting may occur on this type of metal due to prolonged exposure to salt, it is much slower to degrade and will retain greater structural integrity for longer periods of time. Even in crevices, where you might expect to see more degradation of the material, marine-grade stainless steel performs well.

Water Temperatures

Marine grades of stainless steel are better at continuing to function at extreme temperatures. In situations where water would normally turn to ice, seawater can remain liquid even at sub-zero temperatures. This means that these types of alloy can be used in the southern extremes of the country and even in offshore settings where they will be exposed to very low cold conditions indeed. Marine grades of stainless steel must be tested for stress corrosion cracking at sub-zero temperatures.

Durability and Longevity

One of the key features of all stainless steel is that it is a highly durable material. The alloy tends to be chosen not just because of its attractive outer sheen but also because it is capable of doing structural jobs that normal steel would be used for. Marine grades of stainless steel afford engineers close to the same level of structural strength as other metals, so there is little to worry about from the point of view of ongoing performance.