Formation of uniform passive oxide layers on high Si content Al alloy by plasma electrolytic oxidation

Preparation of ceramic coatings on an Al–Si alloy by the incorporation of ZrO2 particles in microarc oxidation

“…The peaks at the binding energy of 516.82 eV (2p 3/2 ) and 524.57 eV (2p 1/2 ) from XPS spectra confirmed the formation of V 2 O 3 and V 2 O 5 . A similar result was observed in other reports [11,14]. In addition, the absorption intensity of V 2 O 3 is larger than that of V 2 O 5 from the XPS analysis in Fig.…”

“…5, resolving the nonuniform colorization caused by the variation in oxidation behaviors of Si-rich phases during the casting manufacturing process. This was caused by the dominant component of vanadium oxide at the outer region of MAO oxide layer to effectively cover the Al-rich phase and Si-rich phase, resulting in the formation of a conformal black coating on the entire surface of high Si-content Al alloys [14]. However, the coarsening of the coating was slightly increased as the amount of NH 4 VO 3 in the electrolyte increased from 3 g/L to 6 g/L, as is seen in Fig.…”

“…Because the temperature around the discharge channels can reach 1600-2000 K [12], V 2 O 3 can be formed during the MAO process, leading to black appearance, and further oxidized and turned into V 2 O 5 [13]. Few reports have focused on cast aluminum alloy substrates with a silicon content of more than 10 wt.% [14]. Although a favorable appearance can be achieved using MAO on Al-Si alloys with high Si content in an aqueous solution containing ammonium metavanadate, such V-containing MAO coatings have a thick porous layer and coarse surface [14].…”

“…Few reports have focused on cast aluminum alloy substrates with a silicon content of more than 10 wt.% [14]. Although a favorable appearance can be achieved using MAO on Al-Si alloys with high Si content in an aqueous solution containing ammonium metavanadate, such V-containing MAO coatings have a thick porous layer and coarse surface [14]. This rough and brittle surface is detrimental to tribological performance.…”

Formation of Black Ceramic Layer on Aluminum Alloy by Plasma Electrolytic Oxidation in Electrolyte Containing Na₂WO₄

“…During PEO coating, the selection of the electrolyte was found to be important in tailoring electrochemical reactions which affected the surface characteristics, in particular, including the realization of various colors of the ceramic oxide compounds such as ZrO 2 , 9) Mn 2 O 3 , 10) V 2 O 3 , 11) etc. Our research group also reported that the black ceramic layer on aluminum alloy via PEO coating within the electrolyte containing NH 4 VO 3 was successfully attained, 12,13) but the poor adhesion issue between the substrate and the ceramic layer remained unsolved yet. According to the previous suggestion by Bayati et al, 14) the introduction of WO 3 compounds into the ceramic layer would be effective to achieve the dark black color as well as high bonding strength in aluminum alloys.…”