Only takes a minute crack or bubble to pop on the powder / paint and water gets in then the alloy corrodes (anodises) and you get the horrid white powder stuff appearing and then thats it game over it all blisters and bubbles , best bet blast em and have em redone - about £50 a rim .
My HD rims are ruined from alloy corrosion but getting em sorted is a fortune due to needing new bearings at same time

 

Also not mileage dependant it’s had 5 yrs of road salt and the crud and corruption off the roads and cleaning agents flung on em

 

I think you will struggle with any sort of claim from Renault...a goodwill gesture would likely to be best result.
But it is a 5 year old car and that makes it very difficult to claim any sort of manufacturing defect.
Just as likely to be stone chips or the like that started the rot.
Get hold of Renault Customer Services, they are better bet then a main dealer for anything positive on this.

After that, google local wheel refurbishment companies and see what a refurb would cost.
They may be able to point to common issues on this sort of coating which could strengthen any claim with Renault.

 

I would agree with you if the car was used regularly in Winter it was off the road for eight weeks in December 2016 through January 2017 when the heater motor blew and Renault could not source one in the whole of Europe. Between November 2017 and May 2018 it only covered 1300 miles so I say it has experienced considerably less salt and other crud than most vehicles whose alloys aren't peeling and blistering on every strut. With regards to cleaning agents I always wash the car myself (usually more that I drive it) and used the products supplied when I platinum protection put on the car by the Renault Dealership. Was sold a top to toe protection but when push came to shove surprise, surprise, they hadn't done the alloy wheels.

 

With regards to cleaning agents I always wash the car myself (usually more that I drive it) and used the products supplied when I platinum protection put on the car by the Renault Dealership. Was sold a top to toe protection but when push came to shove surprise, surprise, they hadn't done the alloy wheels.

If you can prove they forgot to coat the rims you can try arguing the products you were recommended could have damaged the paintjob.
BTW what coat it was, I'm considering putting on my car something that will last at least 3 years.