2009-2011 Aveos have the engine oil cooler. When the seals inside the engine oil cooler start leaking (after about 4-6 years), engine oil mixes into the coolant. The engine oil contaminated coolant weakens the rubber in the rad and heater hoses, the water pump seal, and also softens the plastic in the coolant recovery tank. The quality of the coolant recovery tanks isn't the problem. The problem is the oil contamination in the coolant. I also was baffled why the coolant recovery tank in my 2009 Aveo kept cracking until i noticed an oily scum in the coolant recovery tank. Only after i replaced the engine oil cooler was I able to keep the coolant clear and free of engine oil.
That's my 2 cents.
Deano.