About Hard Chrome Coating
Hard chrome is the most rust and scratch resistant coating compared to zinc and black oxide.
About Zinc Coating
Zinc coating offers medium-high rust and scratch resistance and will most likely turn patina/gray over time. Although this affects aesthetics, this does not affect the barbell's performance and function, .
Black Oxide Coating
Black oxide has a great, almost bare-steel feel that lets you feel the knurl on the barbell. Black oxide is least resistant to rusting than hard chrome and black zinc, which may require more maintenance.
LIFETIME CONSTRUCTION WARRANTY
"The knurling of this barbell is very well crafted. The knurl is consistent throughout the entirety of the barbell - something that we look for in high quality bars. The knurling stops just at the collar, so those who grip the bar at its widest, for the snatch, will still have plenty of knurling to hold. The knurling is not too sharp that it cuts up your hands, but it is still aggressive enough to make for a nice contact between hand and barbell. There is no center knurling on the bar so it will serve those who do high volume workouts as well"
- Review on Knurling, Oscillation (WHIP), and Spin provided by The Thirteenth Strength Community