Study on the microstructure and corrosion resistance of ZrO2-containing ceramic coatings formed on magnesium alloy by plasma electrolytic oxidation

Effects of benzotriazole on anodized film formed on AZ31B magnesium alloy in environmental-friendly electrolyte

“…Consequently, the corrosion reactions happen in the anodized film are the progressive chemical dissolution of the anodized film in NaCl solution with pH 7 according to Eqs. (8) and (9):…”

“…Anodization is well known and widely employed to produce an anticorrosion film on the surface of metal substrates, such as titanium, aluminum, magnesium and their alloys [4][5][6][7][8][9][10][11]. Unfortunately, several serious problems are pressing for solution.…”

A study on microstructure and corrosion resistance of ZrO2-containing PEO coatings formed on AZ31 Mg alloy in phosphate-based electrolyte

“…2 and 4), which led the coatings showed better corrosion resistance than the coating formed in K 2 ZrF 6 -free electrolyte. Furthermore, after the addition of K 2 ZrF 6 , there generated some corrosion resistance phase, i.e., MgF 2 and ZrO 2 [13], and according to Liang's study [6], long-term corrosion protection of PEO coating was controlled significantly by the synergistic effect of phase composition stability in aggressive environments. After long time immersion test, the corrosion protection was mainly depended on the phase composition, So the existence of MgF 2 and ZrO 2 efficiently enhanced the corrosion resistance of coatings compared with the coating produced in K 2 ZrF 6 -free electrolyte.…”

“…Recently, many reporters have addressed that PEO coatings which consist of zirconium oxides could be fabricated on magnesium alloys by using the electrolyte containing potassium fluorozirconate (K 2 ZrF 6 ) [6,[12][13][14][15][16][17]. Liang et.al [6] have demonstrated that ZrO 2 coating formed in K 2 ZrF 6 solution could offer a quite longer time protection to the magnesium alloy substrate than traditional PEO coatings fabricated in alkaline phosphate electrolyte due to the higher chemical stability of ZrO 2 .…”

“…Liu et.al [11] have found that the elements distribution in the PEO coating produced in K 2 ZrF 6 -containing is inhomogeneous, and the content of MgF 2 is high in the pores and an MgO-rich layer is evident in the layer near to the Mg substrate. Luo et.al [13] proved that the ZrO 2 -containing ceramic coatings fabricated in K 2 ZrF 6 -NaSiO 3 -KOH electrolyte showed the most superior anti-corrosion properties than that of the other two electrolytes, i.e., Zr(NO 3 ) 4 -KOH electrolyte and ZrOCl 2 -KOH electrolyte, because of its uniform surface, a compact inner layer and the maximum thickness and some corrosion resistance phases. However, the structure and corrosion behavior of PEO coated magnesium alloy fabricated in mutative concentrations of K 2 ZrF 6 -containing phosphate-based electrolyte is still not fully understood.…”