Авіаційно-космічна техніка та технологія (Feb 2024)
Determination of the rate of corrosion of the main structural material of the grids of capillary phase separators
Abstract
The subject of this study is the corrosion processes that occur in the fuel tanks of spacecraft with a long service life, the engines of which operate on chemically aggressive fuel components (FC): nitrogen tetroxide (NT) and asymmetric dimethylhydrazine (NDMH). The goal is to determine the reduction of wire diameters and the increase of cell sizes of capillary phase separator grids (PSG) because of the corrosion effect of the main structural material of the 12X18H10T stainless steel grid. Task: establishing the presence, type, and rate of corrosion of the main structural material of the PSG nets. The methods used are as follows: to determine the presence of corrosion by studying the composition of substances found on the surface of the grids – X- ray fluorescence, X- ray structural, atomic absorption, potentiometric, turbodimetric, infrared spectroscopy, and chromato-mass spectrometry; to determine the type of corrosion-metallographic studies of mesh samples; to determine the rate of corrosion-measuring the geometric dimensions of mesh samples. The following results were obtained. The metal cations detected on the surface of the mesh samples correspond to the elements that make up the alloy of aluminum and steel - the main structural materials of the fuel tanks of launch vehicles; 12Х18Н10Т steel is not susceptible to local types of corrosion (pitting, intercrystalline, dot, contact, crevice, and stress corrosion cracking) in high-pressure and low-pressure tanks; the presence of a continuous (uniform) corrosion effect on the surface of the grid wires was established; dependences of changes in the main geometric parameters of the grids (wire diameters and cell sizes) over time were obtained, according to which the limits of the corrosion rates of stainless steel grade 12X18N10T in the liquid phase of NT and NDMG and in the gas phase were established; and coefficients of the maximum corrosion rate were calculated. Conclusions. The scientific novelty of the obtained results is as follows: for the first time, the presence, type, and rate of corrosion of the main structural material of the PSG grids because of their long-term operation (14...31 years) in the liquid phase of AT and NDMH and in the gas phase were determined using cross-methods.
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