The effect of pulse waveforms on surface morphology, composition and corrosion behavior of Al 2 O 3 and Al 2 O 3 /TiO 2 nano-composite PEO coatings on 7075 aluminum alloy

Effect of Pulse Current Mode on Microstructure, Composition and Corrosion Performance of the Coatings Produced by Plasma Electrolytic Oxidation on AZ31 Mg Alloy

“…By increasing the cathodic width, the big pores produced by E-type of discharging are also eliminated (Figure 4c,d), while the discharge types of C, D and A are prevailing. The limiting of strong discharges with increasing the cathodic duty cycle of bipolar regimes has been reported before [23,24]. For the coatings grown by soft-sparking (B2 and B3) waveforms, the surface morphology reveals a net of micro-pores as a scaffold, micro-cracks and some fine particles dispersed on the coating surface.…”

“…The micro-cracks are usually formed by thermal stresses generated during rapid solidification of molten oxide and the difference between thermal coefficients of the coating and substrate [6,9]. Although the waveform plays a major role on development of morphology in PEO treatment of Al alloys [23,24], the experimental evidences of this work suggest that no noticeable effect on coating morphology of AZ31 Mg alloy occurs by changing the employed waveform. As shown in Figure 3, a uniform surface morphology containing a network of micro-pores, micro-cracks and granules of oxide compounds are evidenced.…”

Corrosion behavior of aluminum oxide coatings created by electrolytic plasma method under different potential regimes

“…Generally, according to the impedance diagrams, the corrosion resistance of the coated specimens increases significantly over the immersion time. Therefore, after 72 hours, the resistance increased to an average of about 10 MΩ [27,28]. Regarding the pulse potential application regime, the corrosion behavior of the samples in the duty cycle of 30% is better than 70%, which can be related to the thickness of the coatings and their porosity percentage [29].…”

Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

“…One of the emerging trends consists in the addition of insoluble particles to the electrolyte, which are incorporated into the surface layer through cataphoretic effects, with the aim of enhancing specific properties or promoting additional functionality. For instance, it has been shown that the coating corrosion behaviour is improved with the addition of ZrO 2 [12] or CeO 2 [13] particles, whereas the incorporation of Al 2 O 3 [14], TiO 2 [15], SiC [16] and SiO 2 [17] improves mechanical properties. Lu et al [18] revealed that the particle uptake from the electrolyte depends greatly on the electrical parameters, more specifically on the frequency of pulsed current used for the coating formation.…”