Right, let's talk about something that doesn't get nearly enough attention when people are specifying street furniture: what you're actually signing up for in terms of upkeep. I've seen too many well-meaning projects install beautiful benches only to have them look utterly neglected two years down the line, all because no one had an honest conversation about maintenance. The cast iron versus steel debate is the classic example. They both sit there in the rain and sun, but they age completely differently, and they demand very different things from you.
Let's start with traditional cast iron. The stuff they've been using since the Victorians put it everywhere. The absolute best thing about it, and I'll die on this hill, is that thick, heavy casting. It's chemically boring, in the best way. When moisture and air hit it, you get surface rust, not structural cancer. It oxidises incredibly slowly because the metal is so dense and there's so much mass. A cast iron bench that's been left to the elements for fifty years might look like a relic from a ghost garden, all pitted and orange, but take a wire brush to it and you'll find solid metal underneath, ready for another half century. That's the core of its maintenance philosophy: it's forgiving.
What that means in practice is that your routine maintenance is almost non-existent if you can embrace the natural look. An unpainted cast iron bench in a park will develop a stable, even rust patina that actually protects the metal from further decay — that's the "pre-rusted" or Corten-style logic, except it's real aged iron. Your job is simply to make sure leaves and debris aren't piling up and holding damp against the legs. A quick seasonal sweep and maybe a poke at any deep pockets of wet muck with a stick. That's honestly it for years at a time. The bench will turn a deep, umbrous brown-orange and sit there perfectly content.
Of course, most people don't want that look. They want a classic black or dark green bench. Fine, but now you've introduced paint into the equation. Cast iron is fantastic at holding paint because that rough, as-cast surface is like a key for primer to grip onto. A high-quality two-pack epoxy paint job from the factory should last a solid three to five years before you even have to think about it, and even then, the first failures will be tiny mechanical chips on the armrest edges or the feet where mowers knock into it. Touch-ups are straightforward: sand back the rust bloom to bright metal, dab on zinc-rich primer, and feather in your topcoat. A full repaint on a bench that's been properly maintained? You might do it once a decade. If you ignore the chips, the rust will creep under the paint film and you’ll have a weekend of scraping and re-painting, but again, the metal core doesn't care. It's patient.
Now, let's shift to steel. And I mean your common modern steel street bench, typically made from mild steel flat bar or tubular sections, often with a perforated metal seat. The entire game changes because steel is thinner and metallurgically hungrier. Mild steel rusts aggressively. It's not a stable patina; it's a progressive exfoliation that will flake and pit and eventually thin the metal to the point of sharp, dangerous holes. You cannot leave a modern steel bench unpainted. It will not patina gracefully like heavy cast iron; it will just disintegrate. Your maintenance schedule is no longer optional — it's the only thing keeping the bench in one piece.
The maintenance routine is therefore dictated by the paint system. A galvanised and powder-coated steel bench starts from a better place — the zinc layer is sacrificial, so a scratch that cuts to the steel will still be protected until the zinc nearby is used up. But powder coat on its own can chip and then trap moisture underneath, allowing the steel to rust unseen until the coating blisters off in a sheet. Your maintenance involves walking around with a touch-up pen of matching enamel, religiously covering every scrape, constantly. You're inspecting welds because that's where the coating is thinnest and rust starts first. You'll find yourself tightening fixings more often because steel has a bit more spring and vibration can loosen nuts. The bench will also heat up and cool down faster than the heavy thermal mass of cast iron, so the paint experiences more expansion-contraction stress.
And then there's the vandalism and wear factor. A cast iron bench can have a slat burned or a leg graffitied, and you can sort out the surface and repaint without any loss of strength. A thin steel tube that's been dented or cracked is more trouble; water gets inside, rusts from the inside out, and one day someone sits down and feels a disconcerting wobble. Repairs often mean welding, which completely burns off the surrounding coating, and you're back to a bare, vulnerable patch that needs immediate re-protection.
I always tell people to think about the long cycles. A municipal parks department might have a crew that sandblasts and repaints every bench in the borough on a ten-year rotation. For them, cast iron is a dream because even if they're a year late, the bench is structurally sound. For a private estate or a university campus where the grounds team is trying to keep everything looking pristine, the lighter steel bench might be easier to physically move for repainting (two people can lift it), but it will need attention in that crucial five-to-seven-year window, without fail. Miss it, and you're writing a purchase order for a new bench, not just another tin of paint.
In the end, the maintenance question isn't really "which is less work," but "which failure mode can you live with." Cast iron's neglect looks like a romantic, weathered piece of the landscape that just needs a quick aesthetic refresh when you get to it. Steel's neglect looks like a hazardous, shabby eyesore that needs to be budget-replaced. I know which one I'd rather explain to a board of directors five years down the road. Think of cast iron as that old friend who can wear a threadbare jacket and still look dignified. Steel is the one who needs a sharp suit at all times, or everyone notices. Choose based on the kind of custodian you're realistically going to be.