What was found
THE ALUMINUM LINE WAS AN OIL PRESSURE LINE RUNNING FROM THE FIREWALL TO THE OIL PRESSURE GAUGE. IT IS LOCATED BEHIND THE INSTRUMENT PANEL IN A VERY HARD TO SEE AREA AND FOUND CORRODED AND DEEPLY PITTED. DISCOVERED DURING ANNUAL INSPECTION. SUBMITTER STATED CAUSE OF CORROSION WAS A DEFROSTER DUCT DIRECTLY ABOVE THE LINE AND TOUCHING IT. THE DEFROSTER DUCT WAS THE OLD STYLE SCAT TYPE DUCTING THAT WAS MADE OF COTTON MATERIAL AND IRON FORMING WIRE. OVER THE YEARS, COTTON DETERIORATED AND IRON WIRE RUSTED FROM MOISTURE AND BEGAN TO POKE THROUGH THE COTTON ALLOWING RUSTED WIRE TO CONTACT ALUM LINE CAUSING A DISSIMILAR METAL SITUATION AND CORROSION.