I understand that it is a powder coat and it flakes off because of oxidation of the cast metal underneath.
I had this problem on my 2014 Plus 8, and took a decision to swap for ones refurbished my the Morgan dealer in Germany, Morgan Park.
The new ones are chrome and look wonderful... this photo shows them off well.
Morgan Park will send the chromed pillars, you have to send back the old ones by return. If you don't, they invoice you the Morgan price for a new pair and charge to the card you used to pay for the chrome ones.
Fitting the new pillars I was taken a back by the way the pillars are fitted to the car: 3 x M5 studs on each side wouldn't to anything to support the screen in an accident. It was that discovery that resulted in me fitting the roll over bar behind the seats.
