My heater core was leaking when I got my ten09. Upon inspecting my radiator, it had mounds of white sand like material around each tube. Took it out to have out cleaned and was told it was bad as there was white sand like on the outside tubes as well where it was leaking. Ordered an aluminum radiator and installed a new heater core.
That's when I learned about electrolysis corrosion. Doing some research I found you get it hot, put your - voltage test meter wire on the negative battery terminal and the + into the colorant. Info said .03 volts was bad, mine was .08 volts. I flushed and cleaned the system, added orange anti-freeze and grounded my radiator at the low fluid sensor.
It seems to be a common problem when the anti-freeze is not serviced as required.
Good luck