Microplasma oxidation is a promising method of producing ceramic coatings for various purposes [1–5]. At present theoretical models of breakdown and coating growth are being actively developed and new application areas suggested [6–8]. We already know the mechanisms of growth of microplasma coatings due to electrochemical and chemical oxidation of metals and inclusions of electrolyte elements in the course of thermal reactions on the surface [9]. In the place of microarc discharge on the solutionmetal interface during a short period of time (about 200–1000 μs) high temperatures of 103–104 K and pressure of 102–103 MPa are developed [10] which result in the formation of a vapor-gaseous medium in the space and the local fusing of the base metal, which is ejected by the arc process into the solution where part of it is hydrated and the rest of it remains there in ionic form [11]. The present article shows additional mechanisms of inclusion of electrolyte components into the microplasma coating composition as a result of crystal formation in the electrode layer. Specimens of 2024 aluminium alloy (4.4% Cu, 0.6% Mn, 1.5% Mg) with a total area of 0.02 dm2 served as anode. They were first etched in potassium hydroxide solution and then purified in nitric acid solution. A plate of stainless steel 3 dm2 in area, served as a cathode. The treatment was carried out in electrolyte based on sodium phosphate (20 g·l−1) with inclusions of ferrous citrate (10 g·l−1) and surface—active substances (triethylolamine 15 g·l−1). A potentiostatic processing regime with unipolar sinusoidal or pulse voltage ranging from 300 to 520 V was used. The coating formation time took from 20 to 40 min, with an electrolyte temperature of 298–318 K. The micrographs and the element composition data on the coatings were obtained using a JSM 84 scanning electron microscope with a link adapter at the magnification of 1000 times. Average concentrations of components were obtained from an area of 200 × 200 μm using three measurements. The concentrations in the crystal region were determined by focusing a beam to 5 μm in size. A morphology study of the surface after microplasma processing has revealed, in a number of cases, dispersed formations on the coating, including those of a regular geometric shape (Fig. 1). It indicates the crystalline nature of the above structures. The presence of dispersed particles on the coating surface is caused by the characteristic features of microarc oxidation. Ejection of melt, which accompanies a breakdown, and its interaction with electrolyte, result in the formation of both fused parts around pores and various dispersed particles of the amorphous structure weakly connected to the surface. Crystallisation on the coating surface under given physical conditions (high temperatures and pressures ) is unlikely. The formation of crystals deep in the solution is also highly improbable as it is not supersaturated in any component, and is heated during the microplasma process. In order to explain the mechanism of appearance of dispersed formations of a crystalline structure, the following approach has been suggested. When a unipolar electric current passes through the specimen surface, intensive decomposition of water occurs: