To explore the effects of different surface treatment processes on the properties of rare earth magnesium alloys,this study employs Mg-Nd-Zn-Zr rare earth magnesium alloy as the research subject and conducts surface modification by using three processes: phosphate conversion treatment,direct electrophoresis treatment,and phosphate-electrophoresis composite treatment. The surface morphology,coating uniformity,coating adhesion and corrosion resistance of the treated samples are systematically evaluated by scanning electron microscopy (SEM),eddy current thickness gauge,pull-out adhesion tester,electrochemical techniques and salt spray test,respectively. The results show that the phosphate conversion treatment forms a thin coating with microscopic cracks on the surface;the coating formed by direct electrophoresis treatment has pores between the coating and the substrate;while the phosphate-electrophoresis composite coatings are closely combined with the substrate without obvious cracks or pores. The adhesion force between the phosphate-electrophoresis composite coatings and the substrate is the highest,mainly because the phosphate conversion treatment not only increases the surface roughness of the substrate,but also the microcracks on the surface are conducive to the penetration of the electrophoretic coating into the interior. The results of electrochemical and salt spray tests show that the corrosion current density of the phosphate-electrophoresis composite coatings is the lowest,the capacitive arc radius is the largest,and the surface morphology has no obvious change after 144 h of salt spray test,demonstrating excellent corrosion resistance and durability.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |