The role of cathodic current in PEO of aluminum: Influence of cationic electrolyte composition on the transient current-voltage curves and the discharges optical emission spectra

• Published in: Applied surface science 2017-02, Vol.394, p.323-332
• Main Authors: Rogov, A.B., Shayapov, V.R.
• Format: Article
• Language: English
• Subjects: Alternating current; Aluminum; Aluminum alloy; Anodic; Cathodic polarization; Cationic; Cationic composition; Cations; Current-voltage curves; Electrolytes; Hydroxides; Optical emission; Oxidation; Sodium
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.10.115

•Hysteresis in anodic current-voltage curve is specific feature of PEO under alternating polarization in the presence of Li+, Na+, K+ cations.•Singly charged cations are required for α- and γ-Al2O3 crystalline phase formation.•There are reciprocal processes under anodic and cathodic polarization. In this paper, the influence of cationic electrolytes composition on electrical and optical responses of plasma electrolytic oxidation process of A1050 aluminum alloy under alternating polarization is considered. The electrolytes consist of 0.1M boric acid with addition of one of the following hydroxides: LiOH, NaOH, KOH, tetraethylammonium hydroxide, Ca(OH)2 up to pH value 9.2. Coatings microstructure, elemental and phase compositions were studied by SEM, EDS and XRD. It was shown that the hysteresis of anodic current-voltage curve (specific feature of “Soft sparking” PEO) was clear observed in the presence of sodium and potassium cations. It was found that composition of microdischarges plasma is also affected by the nature of the cations. It was shown that there are a number of reciprocal processes, which take place under anodic and cathodic polarization.