i need a few ring terminals and screws - are the inexpensive ebay screws and ring terminals known to break?
its going to connect with mains to power supply.
I sanded off the tin coating and revealed yellow metal it appears to be copper coated with tin. I need under 2 amps they seem fine.
Many of the ring terminals on mcmaster are also tin coated copper.
Yellow or red?
Copper is quite reddish. If it's yellow it's more likely to be brass, which is prone to metal fatigue and can break if bent couple of times.
It was likely brass.
Are tin coated brass ring terminals even permitted under vde, csa or ul?
With 240grit it was easy to sand the whole terminal away.
It depends on your use case. For temporary stuff I use the cheap "One Hung Low" stuff, but they really are garbage (don't crimp as securely, are super thin and flexible, are much much more likely to snap off or fail). For anything permanent or important (like mains level voltage) I usually get Anchor brand or equivalent quality. They are eye-wateringly expensive, but they are far and away better quality plus they are corrosion resistant since they are made for marine applications. TE makes some great stuff too, check out their "Diamond Grip" line. I believe it is mil-spec.