Are Porsche discs plated?

[twoqu]

Being the owner of some manky 993t discs, I have always been surprised by what looks to be plating of some kind flaking off. I noticed the disc below also has the same problem in the 7 o'clock position!
Any thoughts?

[s2driveruk]

i thought they were cadmium plated but that might just be the bells to avoid corrosion and looking rubbish behind the alloys

[lji86]

as far as i am aware they arent. i often see this on the edges of these disc but not seen that on the face before. the discs look shot anyway.

[goodall]

that normally happens a disc when gets too hot, surface gets hardened/brittle and rate expansion changes and cracks when temperature change occurs and then bits start falling off....

disc looks heavy scored which fits in aswell with its life getting near the end, so could just be fatigue from a long and hard life showing its self