Effect of Tensile Direction on Corrosion Behavior of AZ31 Magnesium Alloy Rolled Sheets

The influence of pre-tensile deformation at different directions on the corrosion properties of AZ31 rolled sheet has been investigated. Uniaxial tensile test with the strain of 6% has been carried out at angles of 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees with rolling direction (RD), respectively. The corrosion behavior of specimens with different deformation directions in 3.5% NaCl solution and 8.5% Na2SO4 solution was measured by immersion test, potentiodynamic polarization method and electrochemical impedance spectroscopy. After immersion tests, the surface characteristics of various specimens were investigated by scanning electron microscope (SEM). Results showed that the tensile directions had a significant influence on the corrosion behavior. With the increase of the angle between tensile direction and RD, the hydrogen evolution rate in the 3.5% NaCl increased first and then decreased. The turning point was A45 specimen with the minimum value of 2.1 mm/y. The similar trends were also observed in the 8.5% Na2SO4 solution. In electrochemical testing, the A45 specimen exhibited the best corrosion resistance with the largest diameter of the impedance arc and lowest self-corrosion current. The further the angle of the specimen deviated from 45 degrees direction, the lower corrosion resistance.