Hydration
Delta 3
The mechanism for aluminium materials is that Al2O3 has an affinity to form bohemite Al2O3.2H2O. It takes less chemical energy to form that hydrated oxide than it does to maintain the chemical bonds to the adhesive, so hydration wins. In the case of the R22/R44 blades, the materials are stainless steels, so naturally the reactions will involve hydration of ferrous/ferric oxides.
I sympathise with 500e. My place is used as a visual beacon because of the christmas lights. I want to start the movement to stuff the Easter Bunny down Santa's throat and fix two problems at the same time!