Do headset and frame metals need to match, or will a steel/aluminum headset get stuck on an aluminum/steel frame? Will a steel headset get stuck on an aluminum frame bike? Will an aluminum alloy headset get stuck on a steel frame bike? I am _not_ asking about carbon frames, by the way. I ask because I have seen some questions about aluminum alloy seatposts getting stuck in steel frames, and I wonder if the same kind of "galvanic pair" issue would cause a steel / "chromed steel" threaded headset to get stuck into an aluminum frame. Would doing this make the headset impossible to replace? Does it even matter if it is impossible to replace if the bike is not extraordinarily fancy? I'm not worried about the short term, but am wondering about best practices when assembling old bikes from scrap parts.

Seatposts have a relatively long length inside the tube, and no way to get a tool to the bottom of the post to hammer it. If you have a proper headset remover tool, I doubt a headset would ever get so stuck. (Even without the proper tool, it's unlikely to be a problem.)

Also, I don't believe there's such a thing as a headset with an alloy bearing race. So if it has alloy cups, they probably have replaceable bearings that fit inside it, so the cups shouldn't ever need replacing.