The best way to completely stop the damage getting worse would be to put an anode some were on your rig. Anodes are frequently (frequently? I mean always) used on aluminium camera housings to prevent just this kind of problem and I have just installed one to prevent some corrosion on some new electronics pods in my 15.5
Anodes work and they can be pretty small. The dont have to be touching the corroded area just vaguely near so just one will probably do.
You can get them in all sorts of shapes and sizes from a boat chandlers as almost every boat and boat engine in existence uses them. You could thread one on to an existing jubilee clip or put a band around your scrubber and put one either side or the scrubber near the cylinders between the cylinders and your back. You wouldn't even know they were there, and it would look after all your metal.
Or you could get a plastic housing (sorry bad joke)

Hugh