That's an excellent and very practical question. While metal benches are celebrated for their durability and long lifespan, they are not entirely maintenance-free. Understanding the ongoing costs, both in terms of time and money, helps protect your investment. Primarily, the maintenance required and its associated costs depend heavily on the type of metal and its finish.
For powder-coated or galvanized steel benches, maintenance is relatively low. The main ongoing "cost" is your time for routine cleaning. Using mild soap and water a few times a year to remove dirt, pollen, and bird droppings prevents the finish from degrading. You might spend a small amount on a soft brush and pH-neutral cleaner. The goal is to preserve that protective coating. If the coating gets chipped or scratched, a small bottle of touch-up paint matching the color is a minor expense but crucial to prevent rust from starting.
Untreated or mild steel benches designed to develop a patina, like Corten steel, have almost zero maintenance costs. Their protective rust layer is intentional. However, if you wish to stabilize the look and prevent excessive rust flaking, an occasional application of a sealant might be recommended, involving product cost.
The most significant potential cost comes from neglect. If rust is allowed to establish itself on a non-weathering steel bench, the ongoing cost shifts from prevention to repair. This may involve purchasing wire brushes, sandpaper, rust converter, primer, and paint—a more considerable investment of both funds and labor. In severe cases, professional sandblasting and repowder-coating could be needed, which is a major expense.
Beyond rust, consider the hardware and environment. Periodically checking and tightening bolts and screws (maybe replacing a worn one) is a negligible cost. Placing a bench in a harsh coastal environment will accelerate wear, potentially increasing maintenance frequency and cost.
In summary, the ongoing maintenance costs for a quality metal bench are typically minimal—mostly just cleaning supplies and occasional touch-up paint. The real "cost" is the regular, simple care you provide. By investing a little time in proactive upkeep, you can avoid the substantial expense of major restoration, ensuring your bench remains beautiful and functional for decades. It's a small price to pay for long-term enjoyment.