It's not acid, it's a basic. Alkaline batteries contain potassium hydroxide, which is a strong base. Potassium hydroxide reacts with the aluminum in the light, so some of the residue you scraped off wasn't just cell leakage, it was part of the aluminum battery tube that had reacted with the hydroxide.
I knew that. That's what "alkali" means, after all... but I'm in the improper habit of calling anything corrosive an "acid" because if you tell someone to clean up the "base," it could easily be misunderstood. Blasted homonyms! My bad... I should have used the more generic word "corrosive."
Rayovac has the same repair/replacement policy as Duracell and Energizer. All three companies require you to return the leaking cells with the device to be repaired/replaced, however, so you're probably out of luck in this case.
Good to know Rayovac has the same repair policy... but yeah, out of luck at this point. And the light still works.
I like
half-watt's suggestion. Sounds like it would work well.
This morning I tried the CLR on my E01, which I'd already cleaned up well enough to use when the damage first occurred, but which still had a rough place. CLR didn't do anything for the rough aluminum, but it did eat a little of the blue anodizing! (I hadn't paid much attention before the damage occurred, but E01s are anodized on the inside of the tube.) I don't recommend the CLR for this use.
After the CLR didn't work, I found some very fine aluminum oxide sandpaper (maybe a 400 grit, could even be 600) and used it on the rough place. Much more effective! This "sandpaper" is something like a tough fabric instead of the usual paper, very durable and bendable. It comes in a roll about the width of duct tape, and I have no idea how expensive it is--this was a small strip my Dad, a retired machinist, had given me years ago. I rolled a little section of it up into a small stiff tube and the rough place cleaned up well with vigorous rubbing. This was just a small place near the opening of the tube--a larger place further back might require the cordless drill (if you don't have a Dremel) methods
glockboy and
electrothump mention.
The very fine aluminum oxide sandpaper worked so well that I used it on a Romisen RC-I3 that had also had an alkaline leak (yes, I'm a slow learner). It was slightly easier to reach into the Romisen, but there was more corrosion so it took a while to get it clean. Seems odd to use corroded (oxidized) aluminum to clean up corroded aluminum... but it worked!