Investigation On The Effect Of Nano Silica On The Growth And Corrosion Resistance Of The Plasma Electrolytic Oxidation Coatings On AA1060 Pure Aluminum

In this work,the plasma electrolytic oxidation（PEO）coatings were fabricated on the AA1060 pure aluminum by a self-made WH-1A power supply device.The effects of silica nanoparticles（n-SiO₂）additive and different treatment time（15 min or 30 min）on the structure and corrosion resistance of PEO coatings were studied.The effects of adding n-SiO2 particles into Na2SiO3 electrolyte or（NaPO3）6 electrolyte on the structure and corrosion resistance of PEO coatings were also studied.In this work,the coatings structure was studied by comparing and analyzing the voltage-time curves,phase composition,surface morphology and element distribution,surface roughness,fractured cross-section morphology and element distribution and internal surface morphology.The corrosion resistance of the coatings was studied by comparing and analyzing the potentiodynamic polarization curve and electrochemical impedance spectrum.The results showed that adding n-SiO₂ particles into the electrolyte can shorten the time of phase I of PEO process,increase the breakdown voltage and the working voltage of the whole PEO process;n-SiO2 particles can participate in the formation of the coatings,react with theγ-Al₂O₃ phase in the coatings to form mullite phase,inhibit the formation ofα-Al2O3 phase;when n-SiO2 particles participate in the growth process of the coatings,it will increase the content of Si element on the surface and inside of the coatings,reduce the holes on the surface of the coatings,change the porous and nodular morphology to the pancake structure morphology,increase the thickness of the coatings,increase the volume of the cavity inside the coatings,increase the camber of the dome structure of the fractured cross-section,increase the irregular protrusion size of the internal surface and blur the boundary of the irregular protrusion.n-SiO2 particles will affect the corrosion resistance of the coatings by affecting the structure of the coatings,and achieve different effects in different electrolytes.Adding n-SiO2 particles in NaAl O2 electrolyte will greatly improve the corrosion resistance of the coatings,while adding n-SiO2 particles in Na2SiO3electrolyte or（NaPO3）6 electrolyte is not conducive to the corrosion resistance of the PEO coatings.In addition,in NaAlO2 electrolyte,when PEO treatment time was extended from15 min to 30 min,the coatings surface will change from the porous and nodular morphology to pancake morphology,the surface roughness will increase,the coatings thickness will increase,the cavity size will increase,the dome structure arc of fractured cross-section will increase,the irregular protrusion size of internal surface will increase,the boundary of the irregular protrusion will be blurred,and the corrosion resistance will decrease.