Quantitative correlation between geometric parameters and stress concentration of corrosion pits

Pitting corrosion damage often occurs in aluminum alloy structures and can significantly reduce the service life of structures and cause structural failures. In this research, three-dimensional corrosion pit morphology of 7075-T6 aluminum alloy was observed with the Sensofar PLμ confocal imaging profiler and scanning electron microscope. According to the corrosion pit morphology, we systematically investigated the quantitative correlation between the stress state and geometric features of a corrosion pit idealized as a semi-ellipsoidal pit. It is found that the stress concentration factor (SCF) increases with Rs (the ratio of pit width to length) and Rd (the ratio of pit depth to half-length). The maximum possible SCF is independent of Rd and increases linearly with Rs. The SCF of a rotated pit increases with the orientation angle in a cos2θ relation when Rs < 1.0. The empirical equations are also proposed to correlate the SCF to Rs, Rd and θ.