Volumen 64 (2020): Heft 2 (June 2020)

Ni-based coatings can be successfully applied under abrasive and adhesive conditions as a substitute for environmentally harmful chrome coatings. The research has been carried out for thermally flame sprayed Ni-based coatings with remelting (so-called the two-step process) with the different chemical composition of starting powders. The structure of coatings was evaluated by optical and scanning electron microscopy. Both the three-body abrasive wear test, according to ASTM G65-4 (Dry-Sand Rubber Wheel Test) and dry sliding wear test by the Falex tester, were performed. The results show the influence of the effective chemical composition of the metal powders on improving the properties of the coating. The higher hardness of the coatings leads to a lower tendency for the creation of adhesive bonds, and as a result, leads to a lower tendency to scuffing. A similar trend shows the influence of higher coating hardness on the increasing of abrasive wear resistance.

The processes of corrosion-fatigue failure of materials in contact with mineral fertilizers are insufficiently studied. As a result of joint influence of atmospheric corrosion and mechanical loads, about 70 to 80 % of machine parts get out of order, 20 to 25 % of which are failures caused by operating overload due to the strength loss because of atmospheric corrosion. A large part of metal structures of agricultural vehicles used to transport mineral fertilizers is under the direct influence of aggressive environments and dynamic loads that occur during the motion by field roads. Saturated solutions of the most aggressive working environments used in agricultural production, in particular ammonium sulphate and nitrophosphate are investigated to reduce fatigue resistance of ordinary steels groups – St3 and St5 and quality steels – 10 Steel, 15 Steel, 20 Steel, 25 Steel when loaded at all levels. The fatigue endurance limit decreases in comparison with air up to 2.02 times in a solution of ammonium sulphate, and to 2.32 times in a solution of nitrophosphate. In organic fertilizer environments, compared to distilled water, the conditional fatigue endurance limit increased to 9 %. The properties of the given materials as an inhibitor of corrosion-fatigue failure were discovered and proved.

The article deals with the issue of non-destructive testing of riveted joints. In the article, the authors used a non-destructive eddy current array technique, which was applied to detect simulated corrosion in the field of aircraft riveted joints of aluminum sheets. In aircraft maintenance, the eddy current method is used to control the outer surface of the aircraft skin, especially the areas around the riveted joints. This method makes it possible to detect hidden cracks and corrosion that may occur during aircraft operation. Especially hidden are hidden cracks and corrosion of aircraft structures, which cannot be detected during a visual inspection of the aircraft. The aim of the experimental measurements was to reveal simulated corrosion in the area of riveted joints formed on the experimental sample. Corrosion was simulated by gluing aluminum powder to the surface of the aluminum sheets from which the sample was made. The simulated corrosion in the second and third layers of the riveted sample was reliably detected. The settings, the method of control and the results of measurements are given in the article in the experimental part and the results of measurements. Measurements were performed using a defectoscope with an ECA measurement module, with appropriate measuring probes suitable for this type of inspection.

A novel pyridine derivative was synthesized, and its corrosion inhibition effects on mild steel in a 1M hydrochloric acid environment were investigated by gravimetric techniques, The results demonstrated that the inhibitive performance increased with the increasing of inhibitor concentration. At 303, the inhibition efficiency of pyridine derivative 4-hydroxy-3-(pyridin-2-ylaminomethyl)toluene accomplished 96.2% at the inhibitor concentration of 0.005 M. The mechanism of inhibition implicated the forming of a protective layer from inhibitor molecules on the surface of mild steel by a Langmuir adsorption isotherm. The presence of nitrogen and oxygen atoms in the structure of 4-hydroxy-3-(pyridin-2-ylaminomethyl)toluene confirmed by CHN-analysis revealed the adsorption of inhibitor molecules on the surface of mild steel surface.

In this work, a series of Natural Rubber (NR)/Styrene Butadiene Rubber (SBR) blends were formulated to protect metallic petrochemical storage tanks from corrosive media. Therefore, these blends tested against a 10% HCl solution for 72 hr at room temperature. Blends series were prepared with different ratios of NR/SBR; 25/75, 30/70, 35/65, 40/60, 45/55, 50/50, and 55/45. Three types of carbon black (N-330, N-660, and N-762) were added individually to the 45/55 blend. Hardness, tensile strength, modulus, and elongation properties were tested before and after immersion in the 10% HCl attack media. All these mechanical properties decreased after immersion action accept hardness property. Up to 45 phr NR content, the hardness increased linearly independent on immersion action, but HCl immersion gives higher hardness values. Tensile strength increased up to 40 phr NR content with and without immersion and the immersion action decreased tensile values. The highest elongation value obtained with 35/65 blend with and without immersion. The 45 phr NR content gives the higher modulus, while the lowest value obtained with the 30 phhr content. For 45/55 blend, the hardness increased as the carbon black particle size decreased and immersion action gives higher hardness values. The tensile strength decreased linearly with the carbon black surface area, while with the medium surface area, the highest modulus and lowest elongation obtained.