Detection and Quantification of Intergranular Corrosion Around Wing Skin Fasteners Using the Dripless Bubbler Ultrasonic Scanner

Abstract

Corrosion in all its forms is detrimental to the structural integrity of an aircraft and the ability to detect and evaluate the extent of corrosion is of great importance to the airline maintenance community. The U.S. Air Force intends to extend the use of its transport aircraft well beyond their initial design lifetime and therefore has a need for nondestructive inspection (NDI) methods capable of corrosion detection and quantification. One area of concern in these aging aircraft is the corrosion originating from ferrous wing skin fasteners, particularly that which has progressed just beyond the perimeter of the fastener head but not yet visible as exfoliated material. In 1997, ARINC, Inc.[1] examined several NDI techniques for the Air Force Air Logistics Center in Oklahoma City, OK (OC-ALC) in an effort to identify those methods that demonstrate a high probability of detection (POD) and low probability of false alarms (POFA). Electromagnetic, ultrasonic and thermal techniques were applied to wing skin material samples containing corrosion around the fastener countersink [2].