They have built the bridge out of self-weathering rusty steel, something that I have complained about many times because it actually rusts away and can perforate. But they have planned for this, noting:
Weather-proof steel is a steel alloy with a dense corrosion layer, bringing the corrosion process to a virtual standstill. This means the metal can be left exposed. The weather- proof steel, which corrodes about 0.5 mm per 100 years, is 1 mm thicker in all places than would initially be required: after all, steel corrodes on two sides. As such, the bridge has a lifespan of at least 100 years. Furthermore, the robust appearance of the steel fits in well with the atmosphere created by the city's fortifications.