Development of Electrochemical Surface Treatment to Visualize Critical Corrosion-Inducing Inclusions of Zr in Chloride Environments

An electrochemical surface treatment was developed to visualize the corrosion-inducing inclusions of Zr in chloride environments. Pure Zr and Zr alloy (Zr-0.5O-0.5C) were evaluated in this study. The electrochemical surface treatment consisted of repeated galvanostatic anodic polarization and potentiostatic cathodic polarization. After the electrochemical surface treatment, only one brittle and non-conductive shell of Zr oxide was observed at the corrosion initiation site on the tested surface. The corrosion-inducing inclusions were found inside the corrosion pit under the optimum polarization conditions. At the corrosion initiation site on pure Zr, the area inside the corrosion pit contained larger amounts of O, C, and Si than the surrounding matrix. In the case of the Zr-0.5O-0.5C alloy, relatively larger inclusions were observed after the treatment. Extremely large amounts of Si, together with O and C, were present in the inclusions. The inclusions that induced localized corrosion on the pure Zr and Zr-0.5O-0.5C specimens were found to be precipitated, involving the specific aggregation of Si. The surface treatment developed in this study is expected to be utilized as a powerful tool to elucidate the localized corrosion mechanism of Zr in chloride environments.

Obtaining Nickel Concentrates from Sludge Produced in the Process of Electrochemical Metal Surface Treatment

The article presents the possibility of recovering nickel from waste produced as a result of wastewater neutralization during the electrochemical surface treatment of metals. Leaching the sludge with concentrated hydrochloric acid enabled the metals contained in the sludge from precipitate to the solution with the efficiency of 74.4% (Se) to 100% (Zn). The content of elements was determined using the ICP-OES method. The next step was the precipitation of metals from the obtained solution using various reagents. The precipitating reagents used were 0.5 M sodium hydroxide solution, 0.5 M sodium sulphide solution and 1% dimethylglyoxime solution. Selective precipitation made it possible to obtain nickel concentrates with the content of nickel ranging from 15.3 to 98.2% for the first two methods, whereas in the case of the third method based on a dimethylglyoxime solution, the obtained nickel concentrate purity was 94.3%. The process of leaching nickel-dimethylglyoxime complex (Ni-DMG) with sulphuric acid and crystallization enabled obtaining 99.4% purity nickel sulphate, which can be reused in the nickel plating of selected metals. The research shows that waste generated in the process of neutralization of wastewater from electroplating plants is a potentially important source of recycled nickel concentrates.

Ranking of metallic and non-metallic coatings in the electrochemical surface treatment sector

The distribution of coatings by the frequency of their application during surface treatment by electrochemical methods is considered. This is important not only for understanding the structure of the electrochemical surface treatment sector, but also for identifying priority areas of scientific and technical research. Nonparametric statistical methods show the uniformity of samples and reveal the relationship between the number of enterprises that sell a certain type of coating, i.e. the frequency of applying a certain type of coating in different countries (USA, Japan, Italy, France, Germany, Great Britain, Spain, Canada, Mexico, Russia, South Africa). The results of testing the hypothesis of a close relationship between the ranks of coatings showed that a significant correlation was found between the distribution of coatings by the frequency of their application (implementation) among all countries. For example, when comparing the United States and Canada, the rank correlation coefficient is 0.62 (the lowest value obtained), which is greater than the calculated critical value of 0.56; when comparing Italy and Spain, the correlation coefficient takes the highest value of 0.97, which is greater than the critical value of 0.19. The results obtained allowed us to use this data to compile a generalized rating of the frequency of use of all coatings based on data from different countries. Based on the analysis, metal coatings can be arranged in a row according to the descending frequency of their application: Cr > Ni > Zn > Cu > Cd. The results of the ranking of coatings showed that the most commonly used electrochemical methods for surface treatment are metal coatings with chromium and nickel, and among the inorganic non – metallic coatings-oxide and then phosphate, which allows us to highlight the research devoted to the application of these coatings as priority areas of scientific and technical research.

Effect of Current Density on Crystallographic Orientation, and Oxidation Behavior of Copper Plated on Aluminum Substrate

In this work, the electroplating of copper on an aluminum substrate without electrochemical surface treatment was investigated. Electroplating of copper on aluminum substrate was prepared from copper sulfate electrolyte bath with various current densities 1 mA/cm², 3 mA/cm², 10 mA/cm², and 40 mA/cm². The effects of current density on the samples properties were characterized using a different technique. The surface morphology, crystallographic orientation, and corrosion resistance of the Copper film were analyzed using a scanning electron microscope, energy dispersive spectroscopy (SEM-EDS), X-ray diffractometer (XRD), and potentiostat. The samples' surface morphology is changed with different current densities because nucleation is driven by transferring the copper ion rate onto the aluminum substrate. The Cu-10 sample exhibits (111) peak higher and the best corrosion resistance than other samples. Moreover, Cu-1 samples have shifted to positive corrosion voltage (Ecorr) than the other samples.