The temps used in powder coating are not near high enough to affect material strength. Bead blasting, maybe, but I find it very hard to believe. Most chassis are powder coated at the factory. It’s the best, cheapest process for a frame.
Kart chassis do break over time. Over the years, we’ve broken several parts. The Parolin karts always break the seat strut by the motor if you drive them hard enough. I’ve welded several of ours. I’ve also see the strut that holds the tank/steering column break, right at the bend. Drive a kart hard enough, you will break them. If you haven’t broken your kart yet, you need to go faster!!!!!! Just kidding.
Just like seats. Both boys break their seats the first time out. Jeff always breaks them right in the top center back. Greg breaks them on the side. They usually break in the first session. We get 6 months tops out of a seat.