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The method of plasma electrolytic oxidation (PEO) allows for significantly enlarging the sphere of practical application of metals and alloys by modifying their surface properties. PEO coatings, characterized by their good adhesion to substrate and by their developed surfaces, may be an appropriate base for obtaining of composite layers containing polymer materials. In this connection, the application of polytetrafluoroethylene (PTFE) is of considerable interest due to the practical importance of the properties of this fluoropolymer. The method of polytetrafluoroethylene residue utilization developed in the Institute of Chemistry of the FEB RAS allows us to obtain superdispersed polytetrafluoroethylene (SPTFE of the Forum grade) with particle dimensions less than 1 µ m by gas-dynamic thermodispersion. This material is promising for obtaining thin composite coatings (CC).At the same time, when subjecting SPTFE to repeated pyrolysis, one can obtain its different oligomeric fractions, which, in turn, may be applied to the structure of composite layers oriented toward specific operating conditions. Since the products of SPTFE pyrolysis differ in fractional composition, morphology, and thermodynamic properties [1], it seems necessary to study the properties of both the fractions themselves and the heterostructures obtained on their basis in detail so the conditions of layer formation characterized by optimum consumer demand qualities can be selected.The present paper is a continuation of previous studies [2][3][4][5] on revealing the influence of different fractions of polytetrafluoroethylene, which is a constituent of composite coatings, on the charge transfer processes at the oxide heterostructure/electrolyte interface in order to develop a high-performance method of heatexchange surface protection from the deleterious effect of an aggressive medium, including scale formation. It was established in [3,5] that the fractional composition of PTFE and modes of heat treatment (HT), particularly its duration, render the determining influence on protective properties of composite layers. The following fractions of polytetrafluoroethylene were applied in [5]: low-temperature fraction (ltf) educed from PTFE when heated at 70 ° C; high-temperature fraction (htf), which is a residue obtained after heating the initial PTFE to 300 ° C; and PTFE fraction of averaged composition (afc).In the present paper, there was an attempt to study samples with composite coatings containing two intermediate PTFE fractions educed at 90 ° C and in the temperature range 300-314 ° C. Since the most homogeneous and intact CC on PEO structures are formed as a result of heat treatment, optimum modes of HT with differing fractional compositions of applied fluoropolymer were additionally sought.As was been shown earlier [2][3][4][5], composite coatings have complex structures and they consist of a nonporous underlayer and a porous layer which is partially or completely filled with polymer. It is efficient to study this complex object by electrochemical...

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