I have been amazed how little damage salt water seems to do to heavy guage steel and iron,, but get it inside sheet metal and it disapears almost before your eyes. But alloy is worse. I can remember seeing a adbondoned/ dumped VW beetle where we used to go offroading on a beach, mangroves and dunes.. One week a complete engine, the next you could see the crank in the engine and the gears on the transaxle.But the steel internals were still shiny. The steel was still there at that time.Ummmm....HIGH CARBON, GREY IRON COMPOSITION Cast Iron Rotors are resistant to destruction and weakening by oxidation (rust).
But that HQ ute should be ready for work next week with a wash,, and wheels!
When I used to run at Speedway City which was watered with salty bore water every chip and scratch went rusty, the alloy went white. That when washing the car thouroughly the following morning. And box sections have been known to rust out over a short time.
and as Peter said dirt and muck get into places you would never expect.