BlueEagle,
You are correct in regards to the effect of over stressing aluminium alloys as used on leading slats/flap and engine inlet cowls on large commerical aircraft.As temperature is increased the coating of pure aluminium(used as it is more corrosion resistant than a blended alloy) begins to react as it has a lower melting point than a blended alloys.The pure aluminium`s strength rapidly reduces as does its resistance to corrosion with an increase in surface tempertaure.
Most Boeing aircraft( i will use the B737NG as an example) have a thermal overheat switch that will shut off wing anti-ice on the ground to prevent thermal distress to the surfaces that have anti-ice protection.Engine Nose Cowl Anti ice has pressure and temperature protection that functions during all phases of operation.
In flight however, the wing anti-ice thermal switches are isolated as this gives the flight crew the facility to anti-ice in all flight conditions as ice has been known to form in many differing atmospheric conditions and it is more of a priority to de/anti-ice than worry about thermal stress of metals.
The requirement to select wing anti-ice off at +11 degrees is to protect the metals from overheating as the airflow at this OAT will not have enough cooling effect to prevent this stress to the metals.
Regards DDG