Protecting Aluminum from Atmospheric Corrosion via Surface Hydrophobization with Stearic Acid and Trialkoxysilanes

The possibility of subjecting aluminum to hydrophobization and superhydrophobization (SHP) with ethanol solutions of trialkoxysilanes and stearic acid is explored. It is shown that SHP coatings are highly effective in protecting Al against atmospheric corrosion. The thicknesses of surface SHP layers are determined via X-ray photoelectron spectroscopy and ellipsometry. The protective ability of SHP coatings is determined by polarization measurements and corrosion tests in a salt fog chamber.     

Systems of linear differential equations symmetric with respect to transformations nonlinear in a function

We show that if a system of first order linear differential equations with constant coefficients admits an operator whose coordinates responsible for the transformation of independent variables depend on functions then it admits an operator whose coordinates responsible for the transformation of functions depend nonlinearly on functions.     

The conservation laws and group properties of the equations of gas dynamics with zero velocity of sound

All the conservation laws of zero order are obtained by the method of A-operators for a system of n-dimensional (n ≥ 1) equations of gas dynamics with zero velocity of sound. A group subdivision is carried out of this system with respect to an infinite subgroup, which is a normal divider of its main Lie group of transformations; the main group of the resolving system is obtained. First-order non-local symmetries are obtained for the initial system. A special choice of the mass Lagrange variables enables this system to be converted to a reduced system equivalent to it, containing n - 1 spatial variables, which, for n = 2, is written in the form of a one-dimensional complex heat-conduction equation using complex dependent and independent variables.     

Generalized equivalence transformations and group classification of systems of differential equations

The notion of generalized equivalence transformations for which the equivalence transformations considered by Ovsyannikov are universal equivalence transformations is introduced for a system of differential equations. An algorithm of the group classification of the system of differential equations with the help of these generalized equivalence transformations is proposed. The efficiency and advantages of this algorithm are demonstrated by examples of equations of gas dynamics and equations of nonlinear longitudinal oscillations of a viscoelastic bar in the Kelvin model.     

Friedrichs systems for systems of wave equations and shear waves in a three-dimensional elastic medium

This paper considers a two-dimensional hydraulic model which describes gas or oil flow to a horizontal well with hydraulic fractures and takes into account the reservoir geometry and fluid flow between the reservoir and the well. A computational algorithm is proposed, and calculations for gas and oil reservoirs are performed. A comparison of the calculation results and the solutions of the corresponding problems in a three-dimensional formulation show that the calculations using the approximate hydraulic model yield reasonably accurate results.     

Conservation laws and group properties of equations of isentropic gas motion

A system of equations of isentropic gas motion with n ⩾ 2 is classified in terms of zero-order conservation laws with the use of the method of A-operators. New conservation laws are found to be valid only for potential isentropic motion of the Chaplygin gas. In this case, the greatest number of nontrivial conservation laws is obtained, with n scalar conservation laws being nonlocal. Additional properties of symmetry of the considered equations associated with these conservation laws are indicated.     

Sol–Gel Synthesis of SiO<Subscript>2</Subscript> Containers Using Micelles of an Anionic Corrosion Inhibitor as a Template and the Prospects of Creation Protective Coatings Based on Them

It has been shown that silica container particles can be loaded with large amounts of an anionic corrosion inhibitor, sodium N-oleyl sarcosinate, at the stage of the sol?gel synthesis of the particles by using its micelles as a template. When incorporated into paint and varnish coatings, such containers efficiently protect low-carbon steel and D16 aluminum alloy from corrosion under severe conditions of neutral salt spray.     

The Influence of Steel Surface Modifying with Zinc Complexes of Phosphonic Acids on the Efficiency of Its Passivation by Organic Inhibitors

Russian Journal of Electrochemistry - The efficiency of films prepared in aqueous solutions of organic inhibitors on the surface of low-carbon steel preliminarily modified in solutions of zinc...