If you are deciding between an untreated cedar park bench and a powder-coated steel one, the difference in lifespan is dramatic. You are likely asking this because you want something that either looks natural or lasts forever without hassle. Here is the honest breakdown based on real-world conditions.
An untreated cedar bench, left completely bare without any sealant or stain, will typically last only 2 to 5 years in an outdoor setting. Cedar is naturally resistant to rot and insects, which is why people choose it, but without treatment, it is still wood. Rain, snow, and especially ground moisture will cause it to crack, warp, and eventually decay. In a dry climate, you might get closer to 5 years; in a rainy or humid environment, expect it to fall apart after just 2 to 3 years. The primary weather enemies for untreated cedar are constant wetness and direct sunlight, which causes it to gray and split.
In contrast, a powder-coated steel bench offers a lifespan of 15 to 20 years or more, often outlasting the warranty period. The powder coating acts as a thick, baked-on plastic-like shield that prevents oxygen and moisture from reaching the steel. If the coating remains intact, rust does not form. The steel frame itself is incredibly strong and will not rot, warp, or be eaten by insects. The main risk here is physical damage: if a sharp object scratches the coating down to bare metal, rust can start in that spot. However, with minimal care—like touching up a scratch or keeping it away from constant salt spray—it will easily last two decades.
Cedar does have an advantage in aesthetics and feel. It blends into nature and feels warm to the touch. But untreated cedar demands effort: you would have to apply a water repellent or teak oil every year to extend its life to maybe 8-10 years. Most people who buy untreated cedar do not want that chore, so they get the shorter lifespan. Powder-coated steel is more industrial, can get hot in direct sun or cold to the touch in winter, but it is nearly maintenance-free.
So, to answer your question directly: expect an untreated cedar park bench to last 2-5 years, while a powder-coated steel one will last 15-20+ years. If you value longevity and no maintenance, steel wins. If you love the look of natural wood and are okay replacing it in a few years, go with cedar just accept its short life without treatment.