Any trailer I have ever ordered I specify Stainless Steel hardware including screws.
I have friends that have aluminum that have held up well.
I've never considered the ones that you have described, but I can certainly see it would be something to consider,
Don~
I doubt you could specify how the steel is treated. But I'm sure a reputable OEM would use some form of plating.
Just because alum' isn't used, doesn't mean steel is 'cheap'. If it was the ultimate mat'l maybe the axles should be alum' too? Other components come to mind that should always be steel, like couplers. Sarcasm off. Is a direct substitution of alum' for steel on a part a good idea or does it have to be re-engineered to stand up to it's use and/or abuse?
I'm just thinking that just because it isn't alum', doesn't make something inferior.
Reminds me of a segment in DynoTech years ago. Jim Czekala(sp?) told of a customer that had a set of pipes made of titanium thinking it was superior to mild steel & then wrapped the pipes in exhaust wrap to keep them hot while racing. Well that wasnt a great idea as the pipes basically disintegrated inside of the wrap.