The Comparative Analysis of the Coatings Deposited on the Automotive Parts by the Cataphoresis Method

The paper presents preliminary research focused on the determination of the influence of surface preparation on the quality of the paint coating obtained by the cataphoresis method (KTL). The tests were carried out on steel parts used in the construction of trailers and truck bodies. The first research group consisted of cold-rolled and chemically cleaned parts, the second group were mechanically cleaned with abrasive blasting. In order to determine the influence of surface treatment on the corrosion resistance of the tested coatings, besides a corrosion test, roughness measurements were also carried out. Tests were performed on the crude surface and after coating deposition. Moreover, tests were supplemented by measuring the thickness of the coating using the magnetic induction method and the hardness with the use micro and nano hardness testers. Measurements of the tribological parameters under dry friction conditions were performed using a T11 tester. The corrosion resistance of the applied coatings was determined in a salt spray test. The obtained results were compared to those that were determined for different zinc coatings. It has been shown that the method of base steel surface preparation affects every measured parameter and property of tested paint coatings. The quality of the coating deposited on the steel base after chemical cleaning is much better than the one applied to the sandblasted surface. The measured corrosion resistance of the tested paint coatings is only greater than the corrosion resistance of the lamellar zinc coating. The other zinc coatings (galvanic, hot-dip, sherardized) show corrosion resistance by an order of magnitude higher.

Investigation of granulometric, chemical and phase compositions of hot‑dip galvanizing wastes

The article presents the waste generated during the production of hot‑dip galvanizing. The results of the study of the particle size distribution of zinc dust showed that its particle size distribution in the size range of particles ≤ 250 μm, the proportion of which is 87 wt.%, corresponds to the fractional composition of standard powder zinc. In ash, the number of particles up to 250 microns in size is approximately 35 wt.%. Studies of the chemical and phase composition of the hot‑dip galvanized waste – zinc dust made it possible to establish that the zinc content of the waste approximately corresponds to powder zinc (GOST 12601). The proportion of pure zinc in dust is 95 %. Chemical and phase analyzes of the ash have shown that it contains zinc oxides, pure zinc and zinc chlorides. Zinc chlorides, in turn, can be a supplier of chlorine ions in thermal diffusion galvanizing. In this regard, it is of interest to use ash in the composition of the powder composition as an activating and zinc‑containing component. The results of the analysis of the conducted studies of hot‑dip galvanizing wastes – zinc dust and soot show that they are promising for their use as components in saturating mixtures in the production of zinc coatings by chemical‑thermal treatment. This will reduce the cost of galvanized products and ensure the recycling of zinc into industrial circulation.

Directions of the Development of the Metallization of Iron Alloy Products

The article discusses the future of the production of protective coatings based on the hot-dip galvanizing of iron-carbon alloys, such as steel or cast iron. Currently exploited zinc deposits will be exhausted in the next two decades and it will be necessary to start the exploitation of new deposits in order to maintain the supply or quantity of Zn on the global market. In both cases, it will be related to the increasing cost of zinc on world markets. Zinc-based protective coatings (one of the best corrosion protection methods) constitute almost 50% of the world’s zinc consumption. Economic issues with the constant increase in the price of Zn will force the change or modification of hot-dip galvanizing technology. The article presents data on the production, consumption and development of zinc prices on the global market. Possible directions are presented which producers of zinc coatings will have to follow in order to maintain sales markets, such as the modification of chemical compositions of protective alloys which could be an alternative to pure zinc coatings and the possibility of limiting zinc consumption based on the influence of the surface of galvanized elements, i.e. its metal matrix, and surface roughness.

Analysis of methods for obtaining zinc-containing coatings using hot-dip galvanizing production waste

The article presents the waste generated during the production of hot-dip galvanizing. The analysis of the proposed methods of using these wastes in the production of zinc-containing coatings is carried out. It is shown that hard zinc can be successfully used in the compositions of saturating mixtures during thermal diffusion galvanizing of steel products and obtain high-quality coatings. The disadvantages include the need for grinding hard zinc.The dispersed waste of hot-dip galvanizing production, which is formed as a result of blowing pipes with superheated steam, can be used as a cheap substitute for expensive zinc powder in the compositions of zinc-filled paints. For paints, a fraction of 2–15 microns is used, which is 27 % of the total fractional composition. Therefore, in order to use a wider range of values of the fractional composition of dispersed waste to obtain zinc coatings and thus ensure the recycling of zinc into industrial circulation, the authors of this article plan to optimize and develop the compositions of powder compositions and the technology of thermal diffusion saturation of steel products based on zinc-containing waste.

Comparative Study on the Corrosion Resistance of Inorganic Zinc-Rich Coating and Thermal-Spray Zinc Coating

The corrosion resistance of two steel coatings (inorganic zinc-rich coating and thermal-spray zinc coating) was studied in detail by using the electrochemical and salt spray test, and the salt spray corrosion thickness was calculated by the time-varying equation established from the mathematical fitting method. The result show that the corrosion mechanism of the two types of coatings was the same that based on the sacrificed of zinc through anodizing phenomenon. The main reason for the difference of corrosion resistance between the two anticorrosive coatings was that the coating density and shielding effect of corrosion products were different. The 7500-hours salt spray test showed that the corrosion rates and microstructure characteristics of both types of zinc coatings were homogeneous on the premise of ensuring coating reliability. The time-varying equation can be used to evaluate the service life of the zinc coatings and judge their corrosion resistance quickly, that providing theoretical support for the maintenance of steel structures as well as the accelerated selection and design of coating formulations.

SOME FEATURES OF ELECTRODEPOSITION OF METALS FROM ELECTROLYTES WITH SURFACTANTS

for a long time, the use of various surfactants in the composition of simple electrolytes by researchers to improve the quality of metal coatings with cadmium and zinc has been an urgent task.Surfactants contribute to the grinding of the coating structure, the elimination of their porosity and the appearance of anticorrosion properties of coatings. For example, cadmium electroplated coatings require corrosion resistance, since they are operated in tropical climates, in underground tunnels. Zinc coatings are widely used in building structures and roofing, on electrified railways and high-voltage power lines, in the mining industry and water pipes, as well as for galvanizing the body material in modern all-terrain vehicles to pass in hard-to-reach places without being subjected to corrosion. The object of our research is the process of electrodeposition of cadmium and zinc from simple acidic electrolytes with surfactants, which are thiourea derivatives of dialkyl-phosphorous acids in the current density range of 0.5-3.5 A /dm2, at room temperature. To confirm the quality of the obtained electroplating, we used a JSM-6490LV scanning electron microscope with INSA Energu energy–dispersion microanalysis and HKL-Basicc structural analysis systems with a useful magnification of 300000.