I have a friend that had his brick chimney painted about 5 years ago, when they painted the house. Prior to that, the chimney had never been painted, and the house was built in the early 1940's. They painted it because a neighbor had there chimney painted a few years earlier, and they liked the look. The neighbor has just had the chimney replaced, since the brick was cracking as a result of the moisture freezing and cracking off the face of the bricks. This is also happening to my friends home. I have suggest that he just wait till all the faces are back to the original brick look, and then paint it with clear silicone to repel the water. If this doesn't work, then he also is in for a replacement chimney. Brick was never meant to be painted, and it shouldn't be. In the old days, the paint never caused this problem, probably because it allowed the brick to "breath". Today, the modern paints are designed to repel moisture and to seal the back side. Brick acts as a wick, and as a result, it will absorb moisture, and when the moisture freezes, the brick fails.