Protecting bathroom mirror from corroding around the edges

In my bathroom I have a beautiful illuminated LED mirror. It's now 10 years since I originally installed it – and over time, the edges have become de-silvered as the backing coat has corroded and peeled away.

Research into mirror re-silvering tells me that it's not worth it. Besides, some of the corrosion has extended beyond the edges and into the internal workings of the mirror: meaning it's not possible to access the backing coat in those places.

I have been lucky enough to find a replacement mirror from surplus stock: they don't make many of them any more, and I needed the exact model in order to match the mounting points in my tiles.

Before I mount the new mirror, however, I want to do everything possible to prevent the new one becoming similarly corroded. Research informs me that mirror edges corrode in high-moisture environments (like bathrooms) when water condenses on the backing surface and loosens it. I have no option to affix a physical frame around the mirror: its design does not permit that. Therefore I'm looking for some kind of sealant which I could apply to the exposed parts of the backing, in order to protect it from corrosion.

Given how common this problem is with bathroom mirrors, I would have thought that there would be lots of products on the market to do this. However I have only found one single product which is explicitly marketed to protect mirrors from moisture corrosion. This is only sold in Australia, and I'm disinclined to pay the exorbitant postage costs to send it to me in the UK (which are more than the product costs in the first place!)

So – I'm looking for generic suggestions for how to seal my mirror's edges to protect it for many years to come, so it doesn't corrode.