Steven,
As concerned as you are about fatigue failure, please pardon my surprise that you would even consider an aircraft showing obvious corrosion? But, I would agree with your pilot friend, to a point. I doubt that you can find very many of our airplanes with absolutely no corossion. It just depends on where it is manifesting itself to how detrimental it can be. It would warrant further inspection. However, I believe that your lil inner voice has already told you the answer on this particular aircraft.
