The walls and the murals of the tomb have been covered with anti-corrosive chemicals; at one point the tomb included at least one tower, but it is no longer standing.
Because of the relatively low thickness of this intumescent coating (usually in the 350- to 700-micrometer range), nice finish, and anti-corrosive nature, intumescent coatings are preferred aesthetically and performance-wise.
In the latter function, they work at the same time as anti-corrosive agents, as their hydrophobic nature means that water can not reach the metal surface.
Therefore, metal equipment lacking any preventive (anti-corrosive) measures, may become rusted both inside and out, depending upon atmospheric conditions and how much of that equipment is exposed to the air.