One more question, do the holes they drill at Krown void the manufacturers warranty?
The short answer is NO.
The long answer is this: Manufactures do not warranty against surface rust. That is what most ppl hate to see develop on their cars and makes them next to valueless for resale. Manufactures warranty against holes. You can drive any car manufactured today, untreated, around the road salt capital of the world, Owen Sound, and never develop "rust perforation" during the 7 or so years that is the typical warranty. Consequently, the "manufacturers warranty" issue is moot.
Krown keeps the surface rust away and naturally the "rust perforation" along with it. But what it also does is protect and greatly extend the life all the fittings, gas lines, brake lines and so on. Coincidentally, I 'm getting a new Camry drilled tomorrow.