Coolant.
IIRC water soluble coolants have a corrosion inhibiting as well as lubrication capabilities.
ScotOiler – a company that makes motorcycle chain lubrication systems – have a product called FS365 for all-year-round motocycle corrosion protection described as " FS 365 Complete Bike Protector is a water-based corrosion inhibitor, the idea is that you spray it on and the water content carries it into all the hard to reach places of the bike, we’re talking every tiny little gap. The water content then evaporates leaving a film of protection on all surfaces. " This stuff smells like synthetic coolant ! A litre spray bottle costs around a tenner & it can be had from Halfords and motorcycle dealers (or online). A bulk 5 litre refill container full is around £35
I have a bottle, but as I don't ride all year round now I cannot vouch for it's effectiveness. It has been around for a few years now & gets recommended in the motorcycle mags & forums for "year round" riders.
Nigel B.