One of the problems with living in Taiwan is that summers are really, really hot. This wouldn't be a problem, if it weren't for the sweat. Some riders ride without gloves which I thought was worth trying. This is the result.
At the time they broke, I had just stood up to go up a little rise in the road but I wasn't pulling too hard. One side broke off but luckily I didn't crash. I broke off the other side about two minutes from home (but this time I tried to do it).
Presumably the salt from the sweat went onto the bars and since one doesn't remove the tape after every ride, the salt built up and oxidized the bars.
Tips? Check your bars often for signs of oxidation. Replace aluminum bars every year or so. Use carbon bars. Wear gloves.