Performed prepaid maintenance on a 2011 carrier heat pump split system. During inspection found refrigerant levels within spec ,amp draw’s are reading OK ,airflow is good. I did find in the air handler ,the evaporator coil is in pretty bad shape due to heavy corrosion ,pictures are enclosed. Unit is under warranty but will be out very soon. Customer is going to think about the cost of the coil and will let us know what they would like to do. Recommending replacement due to age condition and overall efficiency not to mention future repairs .