Estimation of the protective ability of chromium coatings deposited from sulfate and methanesulfonate electrolytes based on Cr(III)

Voltammetric and impedance techniques are used to determine the protective ability of chromium coatings deposited on a steel substrate from sulfate and methanesulfonate electrolytes based on trivalent chromium. It is found that chromium deposits obtained from methanesulfonate electrolyte have lower porosity and higher protective ability as compared with deposits from sulfate electrolyte. It is shown that, when the thickness of chromium coatings reaches 15 μm, there are no through pores in deposits for both electrolytes and, thus, the maximum degree of protection of the steel support is achieved in an aggressive medium. An equivalent circuit correctly modeling the corrosion-electrochemical behavior of the studied system is proposed on the basis of data of electrochemical impedance spectroscopy, and the values of its parameters are calculated.     

Comparison of the frequency of a He-Ne laser stabilized to the central component of the magnetic hyperfine structure of the F2 (2) line of methane

Translated from Izmeritel'naya Tekhnika, No. 4, pp. 18–20, April, 1989.     

Automated laser IR spectropolarimeter for surface Mueller matrix measurements

A laboratory prototype of a computer-controlled IR spectropolarimeter based on a tunable CO₂ laser and two electro-optical polarization modulators has been designed, constructed, and tested. This instrument is capable of determining 12 of the total of 16 Mueller matrix elements for a sample surface in a spectral range of 9–11 μm. The measurement error for the normalized matrix elements does not exceed 0.02. The principles of optical arrangement and the algorithm of digital processing of the photodetector signal are considered. A procedure for the instrument calibration is discussed. The results of measurements of the Mueller matrix elements for reflection from the surface of polystyrene and water at a wavelength of 9.7 and 10.6 μm are presented.     

Kinetics and Mechanism of Chromium Electroplating from Cr(III) Baths

Kinetics of step-wise discharge of Cr(III) to Cr(0) in electrolytes containing aminoacetic acid is studied. The limiting current of Cr(II) ion discharge to metal is much lower than the limiting diffusion current of Cr(III) reduction to Cr(II), which results in the accumulation of Cr(II) ions in the electrolyte even at the potentials of the limiting current of chromium electroplating. The apparent catalytic effect of OH^–ions during Cr(II) discharge is associated with the formation of electroactive hydroxocomplexes of bivalent chromium. The kinetic equation of the studied process is derived and analyzed. The probable nature of the limiting currents of chromium electroplating is discussed.     

Electrodeposition of nanocrystalline chromium-carbon alloys from electrolyte based on trivalent chromium sulfate using pulsed current

The effect of the parameters of pulsed electrolysis on the current efficiency, nanocrystal size, composition, hardness, friction coefficient, and wear resistance of nanocrystalline Cr-C coatings obtained from electrolyte based on Cr(III) sulfate containing carbamide and formic acid is studied. It is shown that coatings contain ∼9 wt % of carbon; the current density and pulse ratio produce practically no effect on their composition. It is found that a maximum appears on the dependence of current efficiency on pulse ratio in the case of the pulse ratio of ∼1.05–1.1. Thereby, current efficiency greatly exceeds the value implemented in the steady-state current mode. It is shown that, if the microhardness of Cr-C deposits obtained at constant current is close to 850–900 HV, the microhardness may increase to ∼1200−300 HV when pulsed electrolysis is used in certain modes. It is found that application of pulsed electrolysis allows a significant decrease in the friction coefficient of chromium-carbon coating (steel counterbody) both under the dry friction conditions and in the case of boundary lubrication and also results in an increase in the deposit wear resistance.     

Reserves of glass-melting intensification

Translated from Steklo i Keramika, No. 6, pp. 8–10, June, 1989.