For a public park, I’d choose commercial-grade furniture built for heavy use and poor behavior, not residential pieces. The setting combines sun, rain, freeze-thaw cycles, foot traffic, graffiti, and occasional vandalism, so the material and hardware matter as much as the shape. My default is powder-coated aluminum frames with HDPE slats or galvanized steel with concrete. They offer the best balance of durability, maintenance, and repairability.
Powder-coated aluminum is excellent for benches, chairs, and picnic tables because it resists rust and is relatively light for parks staff to move during maintenance. Specify a thick-wall extrusion, UV-stable powder coating, and stainless-steel fasteners. Check the welds and touch-up points; chips are where corrosion starts. For high-theft or high-vandalism areas, galvanized steel frames are stronger and heavier, especially if they are anchored to concrete. They can still rust at scratched edges, so look for good drainage and sealed or capped tubes.
HDPE—high-density polyethylene—is one of the most practical choices for slats and tabletops. It does not rot, splinter, or absorb water, and it handles UV exposure well when the manufacturer uses proper colorants and stabilizers. It is also easy to wipe clean and often has good resistance to graffiti. Recycled plastic lumber should have a reinforced steel or aluminum frame; plastic alone can sag under constant load or heat. Concrete remains hard to beat for immovable benches, planters, and table bases in busy plazas. It is extremely durable and vandal-resistant, but heavy and sometimes harsh in hot sun. For wood, use a proven hardwood such as ipe or robinia, or a thermally treated product, and budget for periodic oiling. Untreated softwood and thin, hollow metal are usually false economies in a public park.
Design details decide whether furniture lasts. Choose smooth, rounded surfaces, anti-graffiti coatings, tamper-resistant stainless hardware, concealed fasteners, and drainage holes so water cannot pool inside legs or frames. Replaceable slats and modular parts help when one component is damaged; the whole bench does not need to be discarded. Anchor fixed seating in high-traffic areas, but leave some movable pieces where flexible gathering is important. Finally, confirm the product is actually commercial-grade, check the warranty, and ask for examples in similar parks. In most public parks, a mix of powder-coated aluminum with HDPE, galvanized steel, and concrete gives the most reliable long-term result.