Salt is a maintenance issue with a cleaning remedy
Airborne salt reaches well inland and deposits continuously on any exposed surface. On metal it holds moisture against the surface, which is what drives corrosion. Fresh water rinsing removes the deposit and, followed by drying, breaks the cycle. It is a genuinely effective control and it costs very little compared with the equipment it protects.
The difficulty is that nobody's cleaning scope usually includes it, because rinsing a roller door track or a set of external fixings does not look like cleaning. It has to be named explicitly with an interval to be delivered. Once it is, the operator gets a maintenance benefit from a line item they were buying anyway for other reasons. Recording the interval against each item, rather than describing external metalwork generally, is what determines whether the task happens at all.
