2205 stainless steel is a metal alloy comprised of specific elements that improve corrosion resistance better than other types of steel. The “2205” refers to the specific alloy used to make-up the material. All stainless steels are in fact made up of various materials like copper and zinc. When you mix different materials and the amount of those materials, you get different alloys, like 304, 316, and 2205. Each of these alloys have different corrosion resistance levels, which the steel industry created an index to measure, called the Pitting Resistance Equivalency Number (PREN).
For an alloy to be fully corrosion resistant to contaminants like salt water, they need to score a 32 or higher on the PREN index. As you can see from the graph below, 316 Stainless Steel scores only at a 25, making it susceptible to corrosion. We still use 304 Stainless Steel, which scores at a 20, but only in interior applications or in environments at least 5 miles from saltwater. On the other hand, 2205 scores at a 34, making it fully corrosion resistant to salt water contaminants.
In short, 2205 Stainless Steel is going to be more durable, longer lasting, and safer in the long-term. That’s why 2205 stainless steel helps bridges that travel over brackish waters and deep sea oil rigs. It’s the best material for the job.
We do not recommend stainless steel posts be used in exterior coastal environments in the Long Island or coastal Connecticut areas, as we have found that to be an extremely corrosive environment that stainless steel cannot hold up to. We recommend using our fluoropolymer powder coated aluminum posts in these environments as they will perform best in extreme conditions.