Clean your yoyos with wet wipes or alcohol wipes when you are done playing with them. Be sure to use a dry tissue to remove the excess water too, as you want to remove the salt from your sweat that has dissolved into the water from the wipes.
I don’t sweat a lot, but I obsessively wash my hands before and sometimes during play because I hate how any sweat or dirt on my hands increases friction between my skin and the string/yoyo. I’ve never heard of anyone having pitting as a result of this (sorry to see that’s the case for you). I’d recommend using Dawn and a little water to wipe it down, as baby wipes could leave residue and I worry alcohol might be too harsh over time (not an expert chemist by any means, though).
I think this isn’t noticed by more people is because it takes years for the corrosion to appear. The Surveillance above is roughly 4 years old, and the Heist below is one of my very first yoyos, so it has been around for 7 years. I have a lot of other yoyos in my collection that have some form of corrosion as well, it’s just that these are the best and most obvious examples.