It's relatively safe, and for the amount going on the edges, I can't see that as any worse than the stuff you use in waxing the bottom of your board.
Krown is designed to slow down or inhibit corrosion on vehicles. It is a petroleum based product with rust inhibitors containing no solvents. In fact the Krown product is environmentally safe, contains no toxins or solvents, is non-flammable, is non-reactive, is non-corrosive, can be sprayed in any weather, remains active, and is not WHMIS controlled.
http://www.krownindustrial.com/msds/MSDS-Krown-KL73.pdf
http://www.krownindustrial.com/pdf/lvr-eng.pdf