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This paper aims to investigate the electrolytic deposition of corrosion-resistant chromium coatings from a trivalent chromium plating bath based on deep eutectic solvent, a new generation of room temperature ionic liquids.

The electrolyte contained chromium (III) chloride, choline chloride and the additive of extra water. The surface morphology was estimated by means of SEM technique. The microstructure of as-deposited and annealed coatings was studied using X-ray diffraction method. The kinetics of the chromium electrodeposition and the corrosion electrochemical behavior of the coatings were investigated by cyclic voltammetry technique.

Chromium coatings with an amorphous type of microstructure are electroplated from this bath. Some carbon and oxygen are included in deposits obtained. The step-wise mechanism of the electrochemical reduction of Cr(III) ions to Cr(0) is detected. The current efficiency in this system sufficiently exceeds that typical of usual aqueous electrolytes. The coatings fabricated using plating bath based on deep eutectic solvent showed enhanced corrosion resistance in an acidic medium: there is no current peak of active dissolution in polarization curve and the corrosion potential shifts to more positive values as compared with “usual” chromium.

The electrodeposition of chromium coatings from an environmentally acceptable trivalent chromium electrolyte, a deep eutectic solvent containing chloride choline and extra water additive has been investigated for the first time.

The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al₂O₃) addition to the chromium (Cr) (III) bath.

Pure Cr and nanocomposite Cr–Al₂O₃ coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al₂O₃ content and particle size were investigated.

Current efficiency increased with Al₂O₃ amount and decreased with Al₂O₃ particle size. Maximum current efficiency was achieved at 25 A/dm₂ for pure Cr and 30 A/dm₂ for composite coatings. Al₂O₃ bath content, current density and stirring rate increased the coating Al₂O₃ weight per cent significantly. Addition of Al3+ bath composition inhibited nanoparticle agglomeration, increasing film homogeneity. Cr–Al₂O₃ nanocomposites showed higher microhardness and better corrosion resistance than pure Cr layer.

Cr (III) is not as toxic and as carcinogenic as Cr (VI) which is widely used for Cr electroplating these days. Low current efficiency and poor product quality are, however, major drawbacks of the former. This paper describes significant improvements obtainable by addition of Al₂O₃ nanoparticles to the Cr (III) bath for increasing the microhardness, the corrosion resistance and the current efficiency of the deposition.

Tin coatings Tin is used extensively because of its high resistance to corrosion in a large number of environments. The greatest use is for the production of tinplate, used in the packaging industry. A low‐carbon steel, in the form of strip or sheet, is given a thin coating of tin on both sides. Two methods are used commercially for producing tinplate—hot dipping and electrolytic plating.

Discusses the various applications of chromium in pre‐paint metal treatments and the restrictions being placed on their use. Gives details on equivalent non‐chromium products.

Fe‐Ni‐Cr Electrolytic coating. The resistance to corrosion of the ternary Fe‐Ni‐Cr alloy is of increasing practical interest (as well as theoretical). In the present case an electrolyte was prepared for depositing this alloy as used in the constitution of stainless steel, Russian mark 1Kh18N9T, or closely approximating thereto. The best results as to stability of electrolyte were obtained with anodes of this steel. Optimum current density at 25° was 15 to 16 amp./sq.dm., and at 40° 18 to 20 amp./sq.dm., the pH being 1.6 to 1.8. Using a diaphragm in the tank it was found that the catholyte becomes alkaline. By due adjustment with salts and keeping the pH at 1.6 to 1.8 good reproducible results were obtained. Current yield did not exceed 18%. Optimum c.d. at 25° to 30° was 10 to 15 amp./sq.dm. If the coatings exceeded 6 µ in thickness there was poor adhesion with the base metal. This improved after heat treatment. In microhardness the coatings were about the same as the alloy. Their corrosion resistance was tested in 5% H2SO4 and shown to be of high order, but due to small cracks in the coating there was solution of the base metal and the coating tended to peel off. Eight references.—P. F. Kalyuzhnaya et al. (Zh. prikl. Khim., 1962, (5), 1057–1065). See also article on the effect of hydrogen sulphide on the electrode potential of stainless steels (Ibid., 1065–1070); 19 references.

The purpose of this paper is to study the effect of chromium content on the microstructure and corrosion resistance of Ni-Cr coating.

Ni-Cr coating was prepared by pulse current electrodeposition with trivalent chromium. On the basis of studying effect of electroplating parameters on composition and morphology, Ni-Cr alloy coatings with various chromium contents were obtained. The microstructure was characterized by scanning electron microscopy, X-ray diffractometer and transmission electron microscopy. Corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques.

Electrodeposited chromium was solidly dissolved in nickel and refined the grain of the coating. With the increase of Cr content, the corrosion resistance of Ni-Cr coating was enhanced, which is due to the formation of continuous nickel hydroxide and compact chromium oxide passive films.

Ni-Cr alloy coating without penetration crack was prepared in trivalent chromium electrolyte, and the mechanism of its excellent corrosion resistance was proposed.

A chromium‐silicon carbide electrodeposited composite coatings were obtained by suspending silicon carbide (SiC) particles in a trivalent chromium plating solution. This composite was improved by adding the synthesized 1‐ethyl‐1‐cetyl‐2‐sulfonate‐4(hydroxy ethyl)‐piprazine (A16) as dispersing agent for SiC. The adsorption of A16 on SiC was determined. The relation between the zeta potential and codeposition of SiC was investigated by studying the effect of the additive (A16) concentration on mobility (dispersion) and the zeta potential of SiC. The results show that the zeta potential of SiC is more positive at critical micelle concentration of the additive and stimulation results from the adsorption of A16 on the SiC particles. Morphology resistance of the coating was determined and compared with free chromium deposits. These results were discussed according to the obtained adsorption isotherm of the additive.

CHROMIUM Composition and properties of cathodic film in deposition. In a solution of chromic acid on the surface of a chromium cathode there may be a film of various kind. Cathodic films of a primary type arise in electrolysis of chromic acid in the presence of SO42− ions, have a macroscopic character, are more or less easily dissolved in the electrolyte without current, and facilitate reduction by chromic acid to metallic chromium. Oxide films (those of second(ary) type) are formed in electrolysis of chromic acid without sulphate ions, or without current through action of chromic acid on the surface of the cathode metal, have a microscopic character, are not dissolved in the electrolyte, and their presence does not facilitate reduction by chromic acid. It was found that the composition of the cathode films of the first type markedly changes with change in the composition of the solution and electrolysis conditions. Increase in current density and concentration of sulphuric acid, and also reduced concentration of chromic acid, increase the relative concentration of trivalent chromium and sulphate ions in the film. A connection was found between composition and strength (stability) of the cathodic films, on the one hand, and the rate of deposition of metallic chromium on the other. (Four references.)—Z. A. Solov'yeva et al., Zh. prikl. Khim., 1962, (8), 1806–1811.

Describes chromium’s importance in nutrition and health, pinpointing its sources in diets and facts about its absorption in humans. Outlines the body’s ability to store chromium and the function of the element. Reports on current recommendations of safe and adequate levels of intake. The symptoms of chromium deficiency are discussed as are the toxic effects of too high an intake. Concludes with recommendations for required further research.