That's a great question, and one that city planners and public works departments think about a lot. The short answer is: modern urban bins are designed to be *highly* resistant to graffiti, but not completely impervious. It's all about making the cleanup fast, cheap, and easy.
Most high-quality public trash bins you see in cities today are coated with a special anti-graffiti coating. This is usually a clear, protective layer that acts as a barrier. When spray paint or markers are applied, the graffiti doesn't chemically bond to the underlying material. Instead, it sits on top of this slick coating. Maintenance crews can then remove it quickly using a specific graffiti remover solvent or, very often, just with a high-pressure washer. The graffiti washes right off without damaging the bin's original color or finish.
The materials themselves also play a big role. Bins made from powder-coated steel, stainless steel, or high-density polyethylene (HDPE) plastic are naturally smoother and less porous. These surfaces don't absorb paint easily, making it harder for graffiti to stick in the first place and much simpler to wipe away.
So, are they graffiti-*proof*? Not exactly. A determined person with the right tools can still deface them. The real goal is vandalism resistance. The strategy is to use materials and coatings that make the act of graffiti frustratingly ineffective and, crucially, make the cleanup process so efficient that the graffiti is removed before it becomes an eyesore or encourages more tagging. This "rapid removal" approach is often the most effective deterrent. It's less about creating an indestructible fortress and more about designing for easy maintenance, saving the city time and money while keeping our public spaces clean.