Guess I will just put a drop of machine oil on cloth and wipe it on once in a while. That sweat is aggressive, it corrodes even aluminum and my old bike has rusty top tube where sweat fell on it.

Those screws on bar stem are usually machined from titanium but then they shouldn't rust. The old one must not have been titanium as they rusted around and mainly inside the hole where hex wrench is inserted, it removed the black paint, or should they be anodized?