355 Radiator Condition

Radiator in F355 has a whitish coating in the middle of the core down to the bottom. The radiator is not leaking. Should it be replaced during a major?

 

The mechanic doing the major is looking with a flashlight through the side of the car into the vents. I will wait until the engine is out and pressure test the radiators, The car does not have a cooling problem except in Arizona summer where the engine temp will rise 3/4s of the way at a stop light.