Yeah man, tell me about it! I know what your friend is experiencing. I just bought a pair of Ernie Ball Cobalt strings (which were $10 bucks), and after playing about a hour or so, I've already started seeing brown rust developing on the strings already! So I guess I will have to try getting Elixir strings. But the thing with Elixir strings is that the High E string would pop on me every time I would play. So I had my worse experiences with those strings. Are there any other brand that are some how coated strings?
Doors are open for discussion
Know that the highest strings (unwound) used by Elixir are no different that any other guitar strings. They have no special coating. Only the wound strings get the coating.
AND those "cobalt" strings you're using have the same deal...NO difference in the unwound strings from regular guitar strings. The unwound strings are the same as normal unwound strings in Ernie Ball's other string sets which is a specially tempered tin plated high carbon steel.
You probably just have a body chemistry that makes keeping strings clean a problem. Change strings more often. Buy reqular quality guitar strings like D'Addario EXL110 (10-46) by the three pack for under $10....and change them as needed.
Most of these expensive guitar strings and coatings flooding the market are like putting high test premium gasoline in your car that runs just as well on regular. Why waste money? Cobalt? Seriously?
There ARE specialty strings that solve problems or make a planned difference like using expensive Thomastik-Infeld strings on a jazz box for the studio. BUT for regular use, follow GTRDAVE's advice and stop eating KFC during set breaks. Wipe down your strings and guitar after use.
If you're breaking any string regularly, have a guitar tech check the guitar to discover why. Save the broken string to show him HOW and WHERE it's breaking. It's a clue. You might have a burr on your bridge saddle. Whatever. Figure out why it's breaking.