Effect of Nano-SiO2 Content on the Performance of Chromium-free Zn-Al Coatings
To obtain chromium-free Zn-Al coatings with good surface morphology and excellent corrosion resistance,0～1.6％nano-SiO2 was added to the coatings.The morphology,thickness,hardness,and corrosion resistance of the coatings were characterized using equipment such as coating thickness testers,surface roughness meters,and microhardness testers to investigate the effect of nano-SiO2 content on the coating performance.The results show that when 0～1.6％nano-SiO2 is added to chromium-free Zn-Al coatings,the coatings are silver-gray color,possessing a smooth,dense,and flat surface with a roughness around 1.0 μm.As the nano-SiO2 contents increase,the coating thickness varies within the range of 45～80 μm,exhibiting a downward trend.Notably,the coating hardness is significantly enhanced,reaching a value of 123.08 HV.Additionally,the coatings have good adhesion,all of which are above IOS-2 level.Furthermore,the addition of nano SiO2 can boost the corrosion resistance of coatings,and it is observed that the optimal corrosion resistance is achieved when the nano-SiO2 addition is 1.2％.
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