That's not baked on castor, that's just varnish which is the last line of defence in a horribly lean run and it'll come off quite easily. But the piston...oh wow...do you fly off a beach or something? Some of those scores are very deep, is there still any plating left on the liner? Either way, you're up for a new piston/liner set unfortunately. If the liner hasn't peeled then I'd suggest you use a BruLine air filter (green filter) to try to stop that happening again.