Development of a performance test protocol for corrosion prevention compounds for aircraft

In the application of corrosion prevention compounds (CPCs), two prime challenges are the lack of a means of performance evaluation and the understanding of the critical properties for the effective protection. This research attempted to investigate those key properties and their influence on CPCs' performance. One result was the development of a suite of test methods to assess performance and key properties.; CPCs' performance on AA7075-T6 was assessed with electrochemical impedance spectroscopy (EIS). Excellent protection was exhibited by CPC-coated surfaces with interfacial impedances above 0.1 Mohms-cm2 or double layer capacitances below 7.6 x 10-8 F/cm 2. In addition, a prediction method was demonstrated based on impedance parameters that showed the feasibility of using data from less than 50 days of exposure to predict the performance after 180 days of exposure.; CPCs provided protection mainly through the formation and maintenance of barrier film. The failure of CPCs is mainly driven by the defects present in the film and at the film/substrate interface.; The free energies for the water displacement process indicated that all CPCs could displace water from both pristine and mildly corroded surfaces. However, severely corroded surfaces were found to be more compatible with water so that CPCs cannot displace water from such surfaces.; Wicking rates were determined in-situ using fiber optic sensors assembled into simulated lap joints. All tested CPCs demonstrated the ability to wick into occluded regions albeit at varied rates. The wicking rates were substantially smaller when water was present in the occluded regions. The gap of the joint had a strong effect on the wicking kinetics of water and CPCs. For vertically-oriented samples, wicking was slower in tight lap structures and increased with increasing gap to a maximum and then decreased with further increases in gap. No maximum was observed for horizontally-oriented crevices.; A simulation of the wicking kinetics was presented. The simulation reproduced the trend of the changes of wicking kinetics with crevice gap that was obtained from experiment. Among the properties that were investigated through the simulation, the viscosity had the dominant effect on wicking kinetics. CPCs with smaller viscosity have faster wicking rates.