What was found
(CAN) DURING WINTER MAINTENANCE, THE BATTERIES WERE REMOVED FROM THE AIRCRAFT, THE CENTE AND LEFT HAND BATTERY BOXES WERE FOUND TO BE BADLY CORRODED. THE FOAM LINE FOR THE RETARDANT SYSTEM WAS FOUND TO BE LEAKING AT THE FITTING ABOVE THE BATTERY BOXES. IT APPEARED THE FOAM HAD ENTERED THE BATTERY BOXES PLUGGING THE DRAINS CAUSING THE MOISTURE TO BECOME TRAPPED INSIDE THE BATTERY BOXES. THE FOAM FITTING WAS TIGHTENED AND THE CORRODED BATTERY BOXES WERE REPLACED WITH NEW UNITS. (X)