Characterization of aluminum alloys environmentally friendly surface treatments for aircraft and aerospace industry

摘要

Due to risk connected to the chromium use, several companies try to find 'true' chromium free products to treat aluminum surfaces. Aim of this work was to evaluate and test some treatment systems for avionics applications, in order to replace standard chromate processes based on CrVI. AA2014-T3 and AA6082-T6 aluminum alloys were subjected to conversion coating processes based on lithium or zirconium salts. Results were compared to those obtained using commercial chromium free products. The electrochemical and corrosion behavior was investigated using the d.c. electrochemical technique and salt spray test (SST). Moreover, in order to be used in some aircraft and aerospace devices, low electrical contact resistance (ECR) is required; these tests were carried out according to a military standard. The results demonstrated that the AA6082-T6 alloy, treated using lithium salts, has passed the SST but did not pass the ECR test. AA2014-T3 alloy treated using lithium salts has passed neither the SST nor the low electrical resistance test.