INVESTIGATION OF THE EXPLOITATION CHARACTERISTICS OF BELLOWS EXPANSION JOINTS MADE OF HEAT-RESISTANT NICKEL ALLOY

Investigations of the macro- and microstructure, mechanical and technological properties of a metal strip made of heat-resistant nickel alloy Cr20Ni43Mo9Mn6Nb-vi were carried out. In order to determine the optimal composition of the pickling solution, studies were carried out on the use of various mixtures for pickling the surface of the strip. On the basis of the studies carried out, technological recommendations were developed for the preparation of materials before welding of bellows expansion joints.

Waste Water from the Production of Titanium Products as a Raw Material for the Ti(OH)4, NaOH and HCl Production

The study of the spent acidic pickling solution (SAPS) processing is presented. The solution is formed in the process of etching titanium products with hydrochloric acid. The processing includes the stages of neutralizing the SAPS with alkali, filtration and drying of the titanium hydroxide precipitate, electrochemical processing of the filtrate containing sodium chloride in an electrolyzer with ion-exchange membranes. The electrolysis process produces sodium hydroxide and hydrochloric acid. The proposed scheme for processing the SAPS makes it possible to obtain titanium hydroxide, sodium hydroxide and hydrochloric acid. Titanium hydroxide can be used in various industries. Alkali can be used in the SAPS neutralization process. Hydrochloric acid after the adjustment is suitable for use in the etching of titanium products.

Optimization of Pickling Solution for Improving the Phosphatability of Advanced High-Strength Steels

This study investigated the optimum pickling conditions for improving the phosphatability of advanced high-strength steel (AHSS) using surface analysis and electrochemical measurements. To remove the SiO2 that forms on the surface of AHSS, 30 wt.% NH4HF2 was added to the pickling solution, resulting in a significant reduction in the amount of SiO2 remaining on the surface of the AHSS. The phosphatability was improved remarkably using HNO3 concentrations higher than 13% in the pickling solution. Furthermore, phosphate crystals became finer after pickling with a HNO3-based solution rather than a HCl-based solution. Electrochemical impedance spectroscopy (EIS) data indicated that the corrosion resistance of AHSS subjected to HNO3-based pickling was higher than that of AHSS subjected to HCl-based pickling. Fluorine compounds, which were involved in the phosphate treatment process, were only formed on the surface of steel in HNO3-based solutions. The F compounds reacted with the phosphate solution to increase the pH of the bulk solution, which greatly improved the phosphatability. The phosphatability was better under HNO3-based conditions than a HCl-based condition due to the fineness of the phosphate structure and the increased surface roughness.

Wastewater Treatment from Galvanization Industry with Zinc recovery

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (<20 %), which makes Zn recovery not profitable. The experimental results presented in this article show that it is possible to use as a coagulant to treat the process wastewaters the spent pickling solution (SPS) from the process, kept separated and added with sodium hydroxide. This results in obtaining precipitates with Zn contents higher than 40%, which brings the further advantage of making Zn recovery profitable.