Don’t take them from Walmart, they are easy to get rusty after a few rainy days. After a Few months with one easy hit, they will feel off. By hit, I mean that I tested with a screwdriver, trying to remove some rust after using wd-40. The same thing happens here in London with daily rains. Had good changes after purchasing another number plate from
https://www.car.co.uk/number-plates and their standard screws besides the plate don’t get rusty at all. I wash my car myself, and it’s minimum once per week. For over 6 months, everything looks as new.