Vintage Horticultural and Garden Machinery Club

I seem to remember being told that the initial layer of oxide/corrosion would protect the underlying metal from further deterioration . That was the theory but in practice it does seem a bit different.
That said, the acids produced by a damp poultice of festering grass (and worse!) does seem to have the ability to corrode things like spindle housings to the point of destruction. “In season” in practical terms there is not a lot that you can do – weekly under deck hosing or pressure washing is not only a messy operation but can have undesirable effects to bearings etc.
Out of season with a dry deck I would suggest dry cleaning with a scraper and stiff brush (not wire) to clean off the crud but leaving the oxide layer and then give the housings a heavy coat of a waxoyl type product or heavy grease to exclude air.
When I was in business we used to coat the underside of “winter service” decks with “soft grease” -a brew much loved by the military back in the 50/60s for coating the underside of “mothballed”equipment and made by mixing heavy grease and engine oil and stirring to a semi fluid consistency and liberally applying with a wide paint brush. Our lubricant supplier used to offer us dented and damaged drums of grease at an acceptable price!

Anything that excludes air and moisture has to be better than nothing . Not sure if I have read your post about galvo correctly but while being fine for steel it is unlikely to be beneficial for aluminium alloys.
My guess is that if money was no object a new bearing housing given a couple of coats of epoxy primer would be the way to go, but to get an existing housing clean enough fot that to be effective would possibly destroy it.
I put a new deck shell onto a little Husky for the brother in law down in Somerset in the summer and fortunately went armed with a pair of good used bearing housings as his were crumbling away to nothing.

I have been using a well known copper grease for years on the Land Rover and have not found any problems.

Like our colleague wristpin I must hold my hand up as someone who has used Copper based anti seize compounds on Aluminium threads and has never noticed any ill effects. I see that Molyslip provide a product named Alumslip for jobs where the presence copper is not wanted but they don’t specify when that might be.
My biggest battle over the years has been trying to persuade people who should have known better that copaslip type products should not be used as the primary lubricant when assembling bearings/bushes.
Here are links to data sheets for two products that I have used successfully for years.

http://www.molyslip.co.uk/anti_sieze_compounds/

http://www.lubadmin.com/upload/produit/FichePDF/lang_1/408.pdf

Slip of the tongue, calling it grease, just the term used in the workshop….. Have seen what happens when its put somewhere it shouldnt be, ie on wiper spindles and wiper ball joints! A guy came in complaining that his newly fitted wiper rods had failed in quite acatastrophic way…… He was amazed when a technician explained the effect copper slip paste has on ball joints and bearings! Was even less happy to be presented with a £270 bill for new rods and links plus labour……