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In the present work, for the first time Zn-Al layered double hydroxide (LDH) nanocontainers were grown in-situ on the surface and in the pores of plasma electrolytic oxidation (PEO) layer and then loaded with a corrosion inhibitor to provide active protection. The developed LDH-based conversion process ensures partial sealing of the pores and provides an effective corrosion inhibition on demand leading to increased fault-tolerance and self-healing properties. The structure, morphology and composition of the LDH-sealed PEO coatings on 2024 aluminum alloy were investigated using SEM, TEM/FIB, XRD and GDOES. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques show a remarkable increase in the corrosion resistance and fault tolerance when PEO coating is sealed with a LDH-inhibitor treatment. Plasma electrolytic oxidation (PEO) is an advanced anodizing process which leads to the formation of ceramic-like coatings on the surface of many light alloys. The coatings form on the surface as a result of short-lived micro-discharges at high voltages in low-concentrated eco-friendly electrolytes.1 The oxide layers developed by PEO are usually hard, strongly-adherent to the substrate and confer both corrosion and wear resistance.2 The properties of PEO layers can be tuned for various applications such as biomedical, photocatalytic, thermal and decorative playing with composition of electrolytes and electrical parameters. [3][4][5] In spite of many advantages, the PEO coatings are usually composed of relatively porous layers as a result of discharge breakdowns and gas evolution during the coating growth. Such an intrinsic porosity of the layer often compromises the barrier properties of even relatively thick coatings. Moreover, the pores are larger as the coating thickness increases in many cases. Several attempts have been made to reduce or seal such porosity. Optimization of current/voltage regimes, 6,7 changing the electrolyte composition including systems with particles, 8,9 different post-treatments 10,11 and duplex coatings 12,13 were tried among other strategies. However, in spite of offering certain improvement to the barrier properties, none of these approaches ensures active protection. Without active protection, the acceptance of PEO coatings for many high demanding applications such as aeronautics is limited. In previous works, a post-treatment immersion of PEO coated Mg alloys into inhibitor containing solution was tried to achieve active protection. Ce 3+14 and 8-hydroxyquinoline 15 were used as corrosion inhibitors. Certain active protection effect was reported though the important issues related to uncontrollable release of inhibiting species were not considered.Recently, layered double hydroxides (LDH) have been widely investigated as environmentally-friendly containers for active corrosion protection of metals, in the form of conversion films [16][17][18][19] and as inhibiting pigments being incorporated into the polymer coatings. 20 The LDH particles offer a twofold effect of ab...

The process characteristics of plasma-assisted electrochemical treatment of iron in aluminate electrolyte consisted of aqueous 0.1 M NaAlO 2 ? 0.05 M NaOH have been studied. It has been shown that in the range of DC voltages from 260 to 340 V, it is possible to deposit dense ceramic-like coatings with the thickness increased from 0.3-0.5 lm after 1 min deposition time to 25-30 lm for 1 h of deposition. The coatings were examined by X-ray diffractometry, Fourier-transformed infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, and an electrochemical potentiodynamic voltammetry. It is shown that in pre-spark conditions (100-200 V) and on the initial stages of micro-arc anodizing the forming films contain, along with amorphous aluminum oxide/hydroxide, a substantial amount of iron oxide/hydroxide. The coatings obtained by micro-arc anodizing at 260-360 V for 10-60 min represent amorphous aluminum oxide with inclusions of crystalline corundum phase. The films with a thickness of 4-15 lm deposited at the anodizing voltage of 320-360 V exhibited the uniformity and good corrosion protection properties after sealing with common agents.

A porous hydroxyapatite (HA)-incorporated TiO 2 coating has been deposited on the titanium substrate using a plasma electrolytic oxidation coupled with electrophoretic deposition (PEO-EPD).Potassium titanium(IV) oxalate is decomposed by micro arcs gener-

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