You make a good point. Wear points, if it has them, would be a problem. The plating condition overall would play a factor as well. If it wasn't plated evenly, one imperfection could let water in. I believe that once that happens, if it happens, it will deteriorate. Just my opinion, of course.
I share your concerns about the T-bar being Zamac as well. I just hope that the designers were cognizant of these issues and their design considered where Zamac was used. It would be interesting to see if there have been any recorded instances of T-bar failure due to water corrosion.