I filled some gaps with cement to prevent water from passing through and then I painted it with the spray. It turned out really well, it adhered very well to the cement. Very good adhesion, as they say, and no water passes through at all (the cement is sloped, of course)

Excellent result and I used it mainly for the car chassis of an 8-year-old car but also a 12-year-old one (the entire surface underneath), which over the years needed a refresh because of snow and salt, it had somewhat lost its color. Depending on the size and the quantity you need, 4 pieces were enough to cover the surface underneath, whereas other brands emptied relatively quickly and were more expensive, so it is more cost-effective to buy in quantity.
When painting underneath, first you want it to be clean and then you need gloves, a mask, goggles, and sodium solvent or gasoline to clean off anything that gets on you. It's good to wear long sleeves and after each coat of the sealant, take a 5-minute break and apply multiple layers for better results when you have a large surface to cover.

Very good, I applied the sealer that I use for my boat, it bonded well with the metal and created a very good surface that doesn't rust at all now. If you have something worth protecting with this, I recommend it! Oh, obviously keep in mind, if you spray it on asphalt, it won't have the same aesthetic surface and car color, as my brother told me, haha