pH is the most important factor, followed by temperature, in determining if water is going to be corrosive or scaling. Keep you pH in line and realize that the hotter the water the faster a chemical reaction (corrosion or scaling) will occur and you should be fine. If your calcium is through the roof then you might want to compensate by running your TA low but it's still the pH that is really going to determine if you have major problems or not. If you let it fluctuate or get out of range you will. If you keep tabs on it and keep it in line you will minimize the risk of problems.