foglights
Military
- Oct 29, 2008
- 18
In my daily work repairing aircraft, I often fine myself wondering how certain hardware stack-ups will be effected by or produce effects on the aircraft in regard to their corrosion properties.
Going through school, we were taught about anodes and cathodes and dissimilar metals and their suseptability to corrosion. I was told that a general 'rule-of-thumb' was to use aluminum washers against the skin of the aircraft regardless of the fastener type to prevent dissimilar metal corrosion. However, while working in a manufacturing setting not too long ago and aircraft building from engineered blue-prints, when installing machine screws or small AN bolts we used a washer of the same material as the fastener unless we were fastening a clamp in which case the washer was the same material as the clamp. Further, when stacking washers for an electrical bonding jumper there is a specific stack of both steel and aluminum washer arranged to prevent corrosion of the aircraft skin. So, obviously there is some consideration given to corrosion prevention when arranging a washer stack-up for fasteners. So, when installing things like steel panel screws or small, steel AN3/AN4 bolts, or even an electrical bonding jumper, where should the material consideration lie, with the surface of the mating materials or the material of the fastener being used?? I am not concerned with specific, stress critical applications. Only general fastening or panels, clamps or otherwise non-critical applications. I hope I have made myself clear.
Thanks
Going through school, we were taught about anodes and cathodes and dissimilar metals and their suseptability to corrosion. I was told that a general 'rule-of-thumb' was to use aluminum washers against the skin of the aircraft regardless of the fastener type to prevent dissimilar metal corrosion. However, while working in a manufacturing setting not too long ago and aircraft building from engineered blue-prints, when installing machine screws or small AN bolts we used a washer of the same material as the fastener unless we were fastening a clamp in which case the washer was the same material as the clamp. Further, when stacking washers for an electrical bonding jumper there is a specific stack of both steel and aluminum washer arranged to prevent corrosion of the aircraft skin. So, obviously there is some consideration given to corrosion prevention when arranging a washer stack-up for fasteners. So, when installing things like steel panel screws or small, steel AN3/AN4 bolts, or even an electrical bonding jumper, where should the material consideration lie, with the surface of the mating materials or the material of the fastener being used?? I am not concerned with specific, stress critical applications. Only general fastening or panels, clamps or otherwise non-critical applications. I hope I have made myself clear.
Thanks