Air abrasion process is used for cleaning casting surface of prosthetic components, and to prepare the surface of these elements for the
application of veneering items. Its side effect, however, is that abrasive particles are embedded in the treated surface, which can be up to
30% of the surface and it constitutes the side effect of this procedure. Such a significant participation of foreign material can not be
indifferent to the properties of the surface. Embedded particles can be the place of stress concentration causing cracking of ceramics, and
may deteriorate corrosion resistance by forming corrosive microlinks. In the latter cases, it would be advisable to remove elements
embedded into the surface. The simplest method is chemical etching or electrochemical one. Nevertheless, these procedures should not
significantly change the parameters of the surface. Among many possible reagents only a few fulfills all the above conditions. In addition,
processing should not impair corrosion resistance of titanium, which is one of the most important factors determining its use as a prosthetic
restoration in the mouth. The study presented results of corrosion resistance of titanium used to make prosthetic components by means of
casting method, which were subjected to chemical processing designed to remove the embedded abrasive particles. The aim of the study
was to investigate whether etching with selected reagents affects the corrosion resistance of titanium castings. For etching the following
reagents were used: 30% HNO3 + 3% HF + H2O, HNO3+ HF+ glycerol (1:2:3), 4% HF in H2O2, 4% HF in H2O, with a control
sandblasted sample, not subjected to etching. Tests demonstrated that the etching affected corrosion properties of test samples, in each case
the reduction of the corrosion potential occurred - possibly due to the removal of particles of Al2O3 from the surface and activation of the
surface. None of the samples underwent pitting corrosion as a result of polarization to 9 V. Values of the polarization resistance, and
potentiodynamic characteristics indicated that the best corrosion resistance exhibited the samples after etching in a mixture of 4% solution
of HF in H2O2. They showed very good passivation of the surface.
This paper presents the findings of fatigue strength tests of 15CrNi6 steel following low-pressure carburizing and oil quenching, subjected to cycles of one-sided three-point bending. The fatigue fractures were compared with the results of fatigue strength studies of 16MnCr5 steel following low-pressure carburizing and nitrogen quenching. The fatigue tests for 16MnCr5 steel were conducted as part of a high-cycle resonance test, with a pendular bending load. The study also involved an analysis of the effects on non-metallic inclusions in the structure on the mechanism of fatigue destruction. The inclusions were found to initiate fatigue cracks. In both cases, a similar method of a fatigue fissure initiation was observed, independent of the study method or specimen material.
The operation of thermal devices and installations, in particular heat exchangers, is associated
with the formation of various deposits of sediments, forming the boiler scale. The
amount of precipitate depends on the quality of the flowing liquids treatment, as well as
the intensity of the use of devices. There are both mechanical and chemical treatment methods
to remove these deposits. The chemical methods of boiler scale treatment include the
cleaning method consisting in dissolving boiler scale inside heat devices. Worked out descaling
concentrate contains phosphoric acid (V) and the components that inhibit corrosion,
anti-foam substances, as well as anti-microbial substances as formalin, ammonium chloride,
copper sulphate and zinc sulfate. Dissolution of the boiler scale results in the formation of
wastewater which can be totally utilized as raw materials in phosphoric fertilizer produc