The short answer is yes—galvanized steel urban planter boxes can rust over time, but they are designed to resist rust for a long time. Galvanizing coats the steel with zinc, which acts as a barrier and also protects exposed steel sacrificially. In normal city conditions, a well-made galvanized planter can last many years, often 15 to 30 years or more depending on coating thickness, design, and environment. It is not rust-proof forever.
Rust becomes more likely when the zinc coating is worn away, scratched, cut, or depleted. Once bare steel is exposed and stays wet, red rust can start. Cut edges, weld areas, drilled drainage holes, and abrasion points deserve attention. If the planter is in soil contact, near salt from roads or coastal air, exposed to constant irrigation, or holding wet soil with poor drainage, the zinc coating will be consumed faster. Acidic soil, some fertilizers, and standing water can also speed up corrosion.
For urban planter boxes, drainage is critical. A box that traps water at the bottom will corrode much faster than one that drains freely. Raising the base slightly, using drainage holes, adding a liner or root barrier where appropriate, and keeping soil from staying waterlogged all help. Avoid scratching the coating during installation, and touch up small damaged areas with a zinc-rich repair paint. Check the box each year for white zinc corrosion, red rust, bubbling coatings, or thin spots.
So, galvanized steel is a practical and durable choice for urban planters, but it should be understood as rust-resistant rather than rust-proof. With good coating quality, proper drainage, and simple maintenance, it can provide many years of service before rust becomes a real problem.