Electrolisis issues asside, it would appear that by far the greatest cause for the failure of radiators and heater cores is the repeated expansion and contraction from the pressurized cooling system. With 16+psi pressure caps being common and automobiles operated through repeated cold to hot cycles daily it’s surprising how durable the current radiators are. In the “good ole days” pressure caps were 6-8psi and the cooling system had a considerable volume of trapped air buffering pressure surges. And, of course, the fan was fixed to the water pump. At idle many cars today are programmed to reach 230* before the electric radiator fan cycles on and at that temperature the pressure is surging above the cap’s opening pressure. Maybe one reason old copper radiators lasted as long as the car was the car didn’t last that long.