A re-understanding of the breakdown theory from the study of the plasma electrolytic oxidation of a carbon steel — A non-valve metal

摘要: Abstract Plasma electrolytic oxidation (PEO) is normally not applicable to non-valve metals. However, in this study, PEO of Q345 carbon steel, a metal, has been carried out under pulsed unipolar regimes aluminate based electrolytes with the addition sodium dihydrogen phosphate understand its coating formation and plasma generation mechanisms. Real time imaging, optical emission spectroscopy (OES), gas collection, scanning electron microscopy (SEM) assisted energy dispersive X-ray (EDS) diffraction (XRD) have adopted characterize processes. It found that cell potential-time responses initiation are affected by surface roughness steel electrolyte agitation, which encountered valve The critical establishment stable discharges thick coatings on steel. thin layer aluminum phosphates (AlPO4 AlPO4·2H2O) or alumina (AAP) at initial stage plays an important role for hence variations associated stability AAP findings paper indicate presence dielectric metal prerequisite occurrence breakdown. Hence, previous models breakdown preceded bubble need be reconsidered.