The short answer is to keep salt off the furniture, stop moisture from sitting on it, and put a protective barrier on surfaces before winter arrives. In cities, outdoor furniture often gets hit by road spray, splash from sidewalks, and de-icing salt tracked around by foot traffic. Salt itself can stain and dry out materials, but the bigger problem is what it does when combined with moisture and freeze-thaw cycles: it speeds up corrosion on metal, breaks down finishes, and pushes water into wood, concrete, and joints.
Start with placement. If you can move benches, planters, tables, or movable seating away from curb lines, salt piles, and heavily treated walkways, do it. Even a few feet can reduce splash and spray. Raise furniture legs slightly with rubber glides, feet, or small stands so they are not sitting directly in salty slush. Avoid piling snow that contains road salt against furniture; that keeps the salt in contact with the surface for longer.
Use covers carefully. Breathable, fitted covers are helpful for tables and chairs that will sit unused, but plastic tarps or tightly wrapped covers can trap moisture and make things worse. If possible, store lightweight chairs, cushions, and fabric items indoors. For fixed urban furniture, a breathable cover plus regular inspection is usually better than sealing it up and forgetting it.
Rinse with fresh water when weather allows. On a mild day above freezing, wash down salt residue with plain water and a soft brush or cloth. Pay attention to joints, feet, welds, and crevices where salt and grit collect. Dry the surfaces afterward if you can, especially metal and wood. Do not use a pressure washer on powder-coated metal, sealed wood, or concrete unless the manufacturer says it is safe, because it can force water into seams and damage the finish.
Give surfaces a protective layer. Powder-coated steel and aluminum benefit from a coat of wax or a manufacturer-approved protective spray, and any scratches should be touched up promptly so salt cannot attack bare metal. Wood should be sealed or oiled according to its finish, and worn spots should be recoated before winter. Concrete and stone can be sealed to reduce salt penetration, but choose a breathable sealer suitable for outdoor use. Fabric and cushions should be brought in or covered with water-resistant, breathable protection.
Choose less damaging de-icing methods near seating areas. If you manage a public space, talk with maintenance crews about using sand or grit for traction near benches and tables, and reserve salt for critical walkways. Clean up salt spills and salty slush rather than letting them sit. After winter, do a thorough wash, inspect for corrosion or cracks, touch up finishes, and reapply protective coatings. A little routine care before and during the salt season will keep urban outdoor furniture looking better and lasting longer.