We present the thermodynamic description of the equilibrium interphase boundary layer on a flat surface active component solution – solid metal as a continuous medium in the case of homogeneity of macroportions interfacial layer at constant temperature and pressure, taking into account the small deformations the surface of the solid phase. Obtained in this specification nonlinear differential equations in partial derivatives (equations of compatibility) are solved analytically in the particular case by reverse setting. According to this decision is based adsorption isotherm equation, which takes into account the deformation of the surface, and the identification of the isotherms at constant parameters is reduced to the Cauchy problem.