The usual definition of a splash zone is the area just above and just below the average water level of a body of water. It also includes areas that may be subject to water spray and mist.
A significant amount of corrosion of fences is due to landscaper tools scratching fence coatings and irrigation sprinklers spraying these damaged fences.  Recycled water typically has a higher salt content than potable drinking water, meaning that it is more corrosive than regular tap water.  The same risk from damage and water spray exists for above ground piping and backflow preventers.  Fiberglass covers, cages, and concrete footings have worked well to keep tools at an arms length. Even the location where a roof drain splashes down can matter.  Drainage from a homes roof valley can fall directly down onto a gas meter causing its piping to corrode at an accelerated rate reaching 50% wall thickness within 4 years.  It is the same effect as a splash zone in the ocean, or in a pool with lot of oxygen and agitation that removes material as it corrodes.
Tanks or structural tubing such as bench seat supports or amusement park rides can accumulate water and moisture if the structure does not allow for drainage.  This humid environment can then lead to internal corrosion of the structure affecting the structural integrity. The same can happen in tropical environments leading to external corrosion. This would include Corrosion in ballast tanks  on ships.