I had my Archer covered in a 'Ceramic coating' by a company in 2016 and again with a 'Nano coating' by another last year. Both were OK but frankly not worth the money, and in the case of the second company I had to ask them to come back as frankly the aircraft looked as shiny as I normally get in two hours with some dry wash/wax bought in Halfords. I didn't really notice any benefit in cleaning and sadly through my own fault entirely I wiped out the Nano coating with a kitchen scourer when removing bugs from the leading edge (Yes, I know that's not a good idea but it's a long story).
Bearing in mind most of these products are being sold for around £600 to £1000 per application you would be as well applying any form of automotive ceramic based gloss yourselves. There are plenty on the market and frankly it will cost you much less. Check YouTube for videos on how to apply them.
Your Arrow will corrode behind the scenes just as fast whether or not you apply any coating. Leaving it outside, especially near any coastline will see you looking at repair bills in a year or two. The benefit you will get is in UV protection from paint fading, but unless you intend to keep the aircraft for many years this won't be your primary concern.
If you can't get hangarage, buy a good aircraft cover, the investment would be more beneficial.