Galvanic corrosion behavior of 7B04 aluminum alloy-CFRP300 under simulated marine environment

Abstract

In order to effectively provide guidance for the selection of aircraft dissimilar metals from the perspective of corrosion protection, the corrosion behavior of typical aircraft lap structures was studied by finite element simulation and corrosion test for the specific service environment of aircraft. The aluminum alloy, composite material and lap joints were subjected to cyclic immersion corrosion test in the laboratory. Then the galvanic corrosion law between aluminum alloy and composite was revealed by polarization curve measurement test, macroscopic and microscopic morphology observation, fatigue test and XRD measurement. Taking the electrochemical parameters measured by polarization curve as boundary conditions, the corrosion simulation model of lap joint was established. After 0 cycle and 10 cycles of cyclic immersion corrosion test, the results show that the self-corrosion potential and self-corrosion current density of aluminum alloy are -802 mV and 2.357×10-7 A/cm2, -872 mV and 1.477×10-6 A/cm2. The self-corrosion potential and self-corrosion current density of composite material are -240 mV and 6.217×10-7 A/cm2, -98 mV and 2.286×10-7 A/cm2, respectively. With the extension of the corrosion cycle, 7B04 aluminum alloy shows a trend of increasing self-corrosion rate and negative shift of self-corrosion potential, while composite material shows a trend of positive shift of self-corrosion potential and slowly increasing self-corrosion rate. The corrosion products of lap joints gradually increase and the corrosion degree becomes more and more serious. With the extension of corrosion cycle, fatigue life decreases and the depth of corrosion pits increases. The corrosion products include Al(OH)3, Al2O3, AlCl3. The simulation results of lap joints are in good agreement with cyclic immersion corrosion test results. The corrosion prone parts of the typical lap structure of the aircraft were given, and the law of galvanic corrosion was revealed, which points out the direction for the corrosion protection of the aircraft structure.

Keywords

• galvanic corrosion
• simulation
• polarization curve
• ccf300/qy9511
• xrd
• fatigue