An investigation of the effect of a magnetic field on the phosphate conversion coating formed on magnesium alloy

In this paper, the influence of the magnetic field on the phosphate conversion coating formed on magnesium alloy has been studied by scanning ion selective electrode technique (SIET), X-rays phase-contrast radiography, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the superposition of a magnetic field during the phosphate conversion coating process can promote the generation of small hydrogen gas bubbles and accelerate their desorption. In addition, irrespective of the microstructure of the AZ91D magnesium alloy, it was found that the Mg2+ cations were distributed comparatively uniformly. A uniform smooth phosphate conversion coating could be obtained by immersion in the treatment solution when a magnetic field was applied perpendicular to the magnesium alloy. It may be expected to use magnetic field to control the formation of phosphate conversion coating on magnesium alloy.