Will excessive cyanuric acid corrode the tubes in a pool heaters heat exchanger?

A pH lower than 7.0, with chlorine or bromine present, will corrode heaters. The lower the pH, the faster it will proceed. That is one of the reasons the pH should be maintained at 7/2-7.8. High levels of cyanuric acid will impede the effectiveness of chlorine. The latest industry research suggests that 50 PPM is the maximum, that should be maintained. If you want to use chlorine and avoid the buildup of cyanuric acid, you should consider a salt chlorine generator. It is the better way to use chlorine.