I've always been leery of this kind of stuff. Strikes me as a bit "snake-oilish". I particularly like this one:
KoolKote is an aerospace quality hard anodize applied to all surfaces of the piston with a buildup of .001". This coating is designed for use in nitro-methane engines such as Top Fuel Drag Racing to endure the corrosive effects of this fuel type.
I've been going to the drags since I was a kid, and have never seen a piston with this coating in a fuel car. To this day, every top fuel or funny car piston I have ever seen is plain, bare aluminum. I mean, c'mon - these guys get maybe 8-12 runs on a piston before it's a souvenier. No piston gets run twice in the same race weekend. They are replaced every run, and the used ones go in the "check" pile, to be dye penetrant inspected back in the shop before they are pronounced "good" for another run. Even with no cracks, they are discarded somewhere between 8-12 runs, depending on how much money the team has. Any sort of coating is going to inhibit this inspection. In other words, this sounds like a load of b.s. from JE. No one is worried about "corrosion" with that short of a service life.
Speaking of which, it strikes me that if any of these coatings are useful at all, it would be in a low service life race motor. Something that gets torn down and freshened up often. Otherwise, I would be worried about this stuff flaking off after too many heat cycles or something like that.
I wonder if anyone has ever done a long term, high milage test on a street engine with any of these coatings. It would be easy enough to coat half the pistons, run it for a few years and a couple hundred thousand miles, and then tear it down to check. I have a hunch there would be no measurable difference between coated and uncoated.