The short answer is to treat the bottom of an urban trash bin as a constantly wet, chemically exposed zone. That is where water, leachate, urine, cleaning chemicals, and road salt collect, so prevention has to combine material choice, design, cleaning, and maintenance.
First, specify a material that suits the location. For wet public areas, HDPE or LLDPE bins are often the simplest choice because they do not rust. If you need metal, use stainless steel in high-salt or high-moisture areas, or hot-dip galvanized steel with a strong epoxy or polyurethane coating. Avoid bare mild steel at the base, even if the bin body is painted.
Second, fix the design. The bottom should not sit flat on pavement where water can pool. Raise it on corrosion-resistant feet or casters, leave a ventilation gap, and slope the base toward a drain hole. A stainless-steel mesh over the drain helps keep debris out. A removable drip tray or sump is also useful because it catches liquid before it sits against the metal and can be emptied and cleaned.
Third, protect every surface. Coat the inside and outside of the base, seal seams, and use replaceable sacrificial base plates where abrasion is heavy. Check that fasteners are stainless or coated as well; a rusty bolt can start corrosion around the mounting point. If the bin has a plastic liner or bag, make sure it does not trap liquid against the bottom.
Day to day, empty liquids promptly, rinse with mild detergent, and let the bin dry before putting a new bag in. Avoid aggressive acid or bleach-based cleaners unless the manufacturer approves them, because harsh chemicals can damage protective coatings. In winter, rinse away road salt and grit more often. During routine collection, look for scratches, chipped paint, and standing water. Touch up damaged coatings quickly, and replace badly corroded base plates rather than waiting for holes to form.
If corrosion has already started, wire-brush the area, apply a rust converter if appropriate, and patch it with a compatible epoxy coating. Then fix the underlying drainage or cleaning problem, or the repair will fail again. In practice, the most effective approach is a corrosion-resistant base, good drainage, and a simple inspection routine that catches small problems before they become structural.