A bit off the original topic, but pressure washing....my take.....
My previous bike, an alloy Bianchi was washed regularly with a hand held sprayer with a soapy solution, then blown down with an airline and then paper towelled properly dry. Did it for ages, no problems I noticed...until I went to adjust my downtube adjusters. Siezed solid. I came to the conclusion the water sitting on them got down the threads. They sheared off trying to turn them, I ended up drilling and retapping them, a hell of a job. All bikes since, I have applied anti sieze to anything with a thread I can get at.
That was the ONLY problem I found with the bike getting washed on a regular basis, and its easily avoided with a little preventative maintenance.