I'd dispute all the way the statement that Macbooks would suffer of corrosion because of normal humidity conditions and need any prevention treatment for long lasting.

It might be true under very extreme and severe conditions, i.e. normally used on a boat sailing on the ocean in tropical waters for years and years but otherwise, unless temperature excursions are very high and may cause inner condensation, experience proved so far that logic boards may well last decades unharmed.

I live a few hundreds meters from the sea side on a very windy island, typical mediterranean climate, and I got around all sorts of Macs manufactured in the last 20 years.

Well, I can tell for sure that not a single board shows signs of corrosion, ancient iMacs and iBooks included. I can also confirm that one week of humid southern winds in autumn is sufficient to trigger Apple's liquid sensors on iPhone's boards that have never experienced any liquid contact.