Morphological characteristics and geometric prediction model of pits in complex corrosion environment

Abstract

For aircraft serving in coastal environments, the aluminum alloy skin is exposed to high temperature, humidity, and salt environment for a long time. Pitting and exfoliation will affect its normal service life. In this article, static salt spray experiments and electrochemical tests were carried out on 2198-T8 Al–Li alloy in nine different corrosive environments. The effects of salt concentration, temperature, and humidity on the corrosion behavior were analyzed and compared. The relationship between corrosion environment parameters and pits was established. The results show that, under the same corrosion environment, the length, width, and depth of the pits all follow the log-normal distribution; compared with the salt concentration and humidity, the increase in temperature has the most obvious promotion on the corrosion rate. Based on the frequency statistics of pit size and electrochemical test results, the pit morphology was simplified to a semiellipsoid geometric model, and the pit size in different corrosive environments was predicted. The predicted size data all fall within the 1.5-fold dispersion region.