Study Of 7075 Alloy Atmospheric Corrosion Test In The Marine Environment

7075 alloy is an important aeronautical material. With the service time increasing, corrosion has become one of limited factors of aircraft safety. The corrosion behavior of 7075 alloy and the problems of similar study at home and abroad were described in the paper. The corrosive environment of 7075 alloy was investigated, which determined the environmental conditions of accelerated test. The development of the corrosion process, corrosion mechanism and corrosion behavior of 7075 alloy were studied. The loss of 7075 alloy mechanical properties after corrosion were tested. This paper made a progress in the following aspects:(1) Marine-atmospheric is particularly severe on corrosion. Salt fog test can simulate the characteristics of Marine-atmospheric. Test conditions such as temperature, salt sedimentation rate, salt concentration and solution pH which affect the test results were studied in the paper, and the most suitable environment for laboratory accelerated test was determined.(2) Periodic spray corrosion test methods were used to test, combined with SEM to record the results. The corrosion behavior of the exposed 7075 alloy, the surface oxide protective film removed 7075 alloy and steel rivets riveting 7075 alloy were record. Alloy corrosion process of the occurrence and development of three test pieces were studied. The results showed that they followed an intergranular law: pitting corrosion, intergranular corrosion and denudation. The corrosion morphology and mechanism were analyzed systematically.(3) The corrosion of 7075 alloy is mainly electrochemical corrosion in the marine environment. Cl- plays a major role in the failure process, the radius of which is small, and it owns good penetration ability, easily penetrate the metal oxide layer and the protective layer into the metal interior then damaging the passive metal.(4) The mechanical properties after corrosion of materials would be changed, and corrosion also affects work life of the structure. The tensile test and hardness test for pre-corrosion test 5 cycle show that 3 # experienced crevice corrosion and galvanic corrosion, and its mechanical properties decrease maximum. The mechanical properties of 7075 alloy can reduce as much as 40%--60% after erosion.(5) After the study of corrosion process and mechanism of 7075 alloy and compared with the experience at home and abroad, effective protective measures were summarized in the paper. For a typical service environment of the aircraft and use, combined with the use of spectrum, reasonable environmental protection and repair measures have been worked out.