Comparison of the corrosion behavior of Aluminum 2024 unclad material to Aluminum 2024 clad in Fiber Metal Laminate applications

Proper design for corrosion control must consider the choice of the right materials and corrosion protection systems. In aircraft industries 2024 clad material is used on exterior areas of the fuselage to improve the corrosion resistance. By using an Aluminum 2024 clad the corrosion is not affecting the core material since the clad layer acts as a sacrificial anode. This concept is also applied for GLARE® Fiber Metal Laminates used in the upper fuselage panels of the A380. While keeping the performance of the Fiber Metal Laminates, leaner and more automated production can help to decrease the costs. One part could be to omit the clad layer on Aluminum.  However this causes questions regarding the corrosion protection system.

Within this study both unclad and clad material will be assessed under galvanic corrosion conditions. To simulate a worst case scenario pre-treated Titanium rivets will be installed into the material without sealant to force galvanic corrosion. In the present work two different laboratory corrosion tests, namely salt spray test using a 3.5% NaCl solution, and a cyclic corrosion test to simulate real in-flight conditions with different temperatures and humidity. The tests specimens will exposed up-to 3000 h respectively 670 h to the ageing tests. Subsequently the samples will examined by light microscopy and cross-section in order validate the corrosion attack. The achieved results will contribute to a leaner and more efficient Fiber Metal Laminate production.