Effect of cathodic micro-discharges on oxide growth during plasma electrolytic oxidation (PEO)

Alexandre Nomine (1, 2) , Julien Martin (3, 1) , Gérard Henrion (1) , Thierry Belmonte (1)

1 IJL - Institut Jean Lamour
2 OU - The Open University [Milton Keynes]
3 Institut de Physique Nucléaire, Atomique et de Spectrométrie

Plasma electrolytic oxidation (PEO) of magnesium alloy is performed in NH4F and alkaline-silicate electrolytes within various waveforms of bipolar current pulses to investigate the role of the cathodic bias on both the growth mechanism of PEO layers and the behavior of micro-discharges. A particular attention is paid to cathodic micro-discharges and their ignition (or not) according to process conditions. Although cathodic micro-discharges have a detrimental effect on PEO layers, cathodic bias is necessary to improve the growth of oxide layers. Conditions that promote cathodic breakdown are discussed and a mechanism of layer cathodic breakdown is proposed. Cathodic micro-discharges, and to a greater extent the applied cathodic bias, influence the anodic breakdown coming immediately after, and therefore, the process behaviour during the anodic bias period.

Domaines: Génie des procédés; Matériaux; Plasmas; Physique des plasmas [physics.plasm-ph]

Alexandre Nomine, Julien Martin, Gérard Henrion, Thierry Belmonte. Effect of cathodic micro-discharges on oxide growth during plasma electrolytic oxidation (PEO). Surface and Coatings Technology, 2015, 269, pp.131-137. ⟨10.1016/j.surfcoat.2015.01.076⟩. ⟨hal-01286241⟩