The corrosion behavior of Mg–Nd binary alloys in the harsh marine environment

Abstract The corrosion behavior of Mg-Nd binary alloys in the harsh South China Sea environment was researched by scanning electron microscopy, energy-dispersive spectrometry and X-ray diffraction analysis. In order to explain the corrosion mechanism, corrosion resistance was analyzed by weight loss rate and electrochemical measurement in the laboratory. With a continuous enlargement of Nd-content, Mg12Nd phases increased and multiplied. The weight loss rate of Mg-0.5Nd alloy was 0.0436 mg•cm−2•y−1 (0.0837 mm•y−1), whereas that of Mg-1.5Nd alloy was 0.0294 mg•cm−2•y−1 (0.0517 mm•y−1) during the exposure corrosion in the South China Sea site. The mechanical strength of Mg-1.5Nd alloy was 148 MPa before the exposure in the harsh marine environment, while the residual mechanical strength was merely about 94 MPa after the exposure test. Both Mg-1.5Nd alloy and Mg-1.0Nd alloy occurred the brittle fracture, which resulted that the elongation was nearly equal to zero. The self-corrosion current density demonstrated that degradation rate of Mg-Nd binary alloys was as follows : Mg-0.5Nd>Mg-1.0Nd>Mg-1.5Nd. For the South China Sea corrosion site, a large amount of sea salts exited in the atmospheric environment. Due to the heavy rainfall and high humidity, sodium chloride in the atmospheric environment dissolved, more serious electrochemical corrosion occurred on the surface of Mg-Nd binary alloys.