Many large metal structures, such as bridges and supertankers, carry vast amounts of paint as protection against the elements.
This needs to be frequently replaced by teams of people doing a difficult and often dangerous job.
Today’s invention is a new type of paint which has a very high oil content. This means that the paint never dries to form a hard outer coating (like climb-resistant paint).
It also allows an army of small robots to roll over the surface continuously, providing much more frequent recoatings than human repainting would allow.
The robots would have magnets to hold them in place and a range of rotary scraping tools with which to scuff off the soft coating.
The paint itself would be made using cheap, heavy oil so the robots could burn it as their fuel source.
The base coat could be a conventionally hard, white one and outer oily coats would be in a contrasting colour so that detecting when the soft protection had been locally damaged or removed would be easy.