Corrosion on my 850 estate

So, virtually no visible corrosion topside on my 1995 850 estate.. there was some underneath toward the rear two years ago but I’ve not had it inspected since by a Volvo specialist... went through the mot today just a few advisories but nothing related to bodywork... the old girl has (genuinely) done lesser than 100k miles and is in great nick, still flys like the proverbial brick... love this car and I’m very keen to reverse and stop any rot, it’s really a keeper... any thoughts and suggestions about corrosion and prevention will be greatly received...

Thanks in advance
Richard