The objective of the presented paper is to investigate the performance of concrete containing volcanic scoria as cement replacement after 7, 28, 90, and 180 days curing. Five performance indicators have been studied. Compressive strength, water permeability, porosity, chloride penetrability, and reinforcement corrosion resistance have all been evaluated. Concrete specimens were produced with replacement levels ranging from 10 to 35%. Test results revealed that curing time had a large influence on all the examined performance indicators of scoria-based concrete. Water permeability, porosity, and chloride penetrability of scoria-based concrete mixes were much lower than that of plain concrete. Concretes produced with scoria-based binders also decelerated rebar corrosion, particularly after longer curing times. Furthermore, an estimation equation has been developed by the authors to predict the studied performance indicators, focusing on the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported as well.
The Ti15Mo alloy has been studied towards long-term corrosion performance in saline solution at 37°C using electrochemical impedance spectroscopy. The physical and chemical characterization of the material were also investigated. The as-received Ti15Mo alloy exhibits a single β-phase structure. The thickness of single-layer structured oxide presented on its surface is ~4 nm. Impedance measurements revealed that the Ti15Mo alloy is characterized by spontaneous passivation in the solution containing chloride ions and formation of a double-layer structured oxide composed of a dense interlayer being the barrier layer against corrosion and porous outer layer. The thickness of this oxide layer, estimated based on the impedance data increases up to ~6 nm during 78 days of exposure. The observed fall in value of the log|Z|f = 0.01 Hz indicates a decrease in pitting corrosion resistance of Ti15Mo alloy in saline solution along with the immersion time. The detailed EIS study on the kinetics and mechanism of corrosion process and the capacitive behavior of the Ti15Mo electrode | passive layer | saline solution system was based on the concept of equivalent electrical circuit with respect to the physical meaning of the applied circuit elements. Potentiodynamic studies up to 9 V vs. SCE and SEM analysis show no presence of pitting corrosion what indicates that the Ti15Mo alloy is promising biomaterial to long-term medical applications.
The paper presents the results of studies of hybrid composite layers Ni/Al2O3/Cgraphite produced by the electrodeposition method. Three variants of hybrid composite layers were prepared in electrolyte solutions with the same amounts of each dispersion phases which were equal to 0.25; 0.50 and 0.75 g/dm3. The structure of Ni/Al2O3/Cgraphite layers as well as the Al2O3 and graphite powders, which were used as dispersion phases was investigated. The results of morphology and surface topography of produced layers are presented. The modulus of elasticity and microhardness of the material of produced layers were determined by DSI method. Tribological and corrosion resistance tests of produced layers were carried out. Realized studies have shown that the material of the produced layers is characterized by a nanocrystalline structure. Incorporation of dispersion phases into the nickiel matrix increases the degree of surface development of layers. Ni/Al2O3/Cgraphite layers are characterized by high hardness and abrasion resistance by friction, furthermore, they provide good corrosion protection for the substrate material.
The work presents the results of the studies of Co-Cr-Mo casting alloys used in the production of frame casts of removable dentures,
crowns and bridges in dental prosthetics. The studies were performed on four Co-Cr-Mo alloys of different contents of Mo, W and other
additives. Electrochemical tests were performed, which aimed at examining the corrosion resistance of the alloys and observing the alloy
structure after chronoamperometric tests with the potential in the area of the occurrence of the passive layer breakpoint. The alloy
microstructure images after chronoamperometric tests show the presence of non-uniformly distributed general corrosion. Moreover, a
project of cobalt alloy casting was elaborated using a ceramic mold casting. Additionally, analysis of the obtained microstructure was
performed. The microstructure of the examined alloys was of the dendrite type. This microstructure was chemically inhomogeneous and
consisted of an austenitic matrix formed by a solid cobalt solution and chromium in the core dendritic structure.
This paper deals with the evaluation of the corrosion resistance of the Al-Si alloys alloyed with the different amount of antimony.
Specifically it goes about the alloy AlSi7Mg0,3 which is antimony alloyed in the concentrations 0; 0,001; 0,005; 0,01 a 0,05 wt. % of
antimony. The introduction of the paper is dedicated to the theory of the aluminium alloys corrosion resistance, testing and evaluation of
the corrosion resistance. The influence of the antimony to the Al-Si alloys properties is described further in the introduction. The
experimental part describes the experimental samples which were prepared for the experiment and further they were exposed to the
loading in the atmospheric conditions for a period of the 3 months. The experimental samples were evaluated macroscopically and
microscopically. The results of the experiment were documented and the conclusions in terms of the antimony impact to the corrosion
resistance of the Al-Si alloy were concluded. There was compared the corrosion resistance of the Al-Si alloy antimony alloyed (with the
different antimony content) with the results of the Al-Si alloy without the alloying after the corrosion load in the atmospheric conditions in
the experiment.
Within the presented research, effect of annealing on nature of corrosion damages of medium-nickel austenitic nodular cast iron castings,
containing 5.5% to 10.3% Ni, was determined. Concentration of nickel, lower than in the Ni-Resist cast iron, was compensated with
additions of other austenite-stabilising elements (manganese and copper). In consequence, raw castings with austenitic matrix structure and
gravimetrically measured corrosion resistance increasing along with nickel equivalent value EquNi were obtained. Annealing of raw
castings, aimed at obtaining nearly equilibrium structures, led to partial austenite-to-martensite transformation in the alloys with EquNi
value of ca. 16%. However, corrosion resistance of the annealed alloys did not decrease in comparison to raw castings. Annealing of
castings with EquNi value above 18% did not cause any structural changes, but resulted in higher corrosion resistance demonstrated by
smaller depth of corrosion pits.
Commercially pure titanium is less expensive, generally more corrosion resistant and lower in strength than its alloys, and is not heat-treatable. The use of Ti and its alloys as construction materials under severe friction and wear conditions is limited due to their poor tribological properties. Nevertheless, proper addition of hard ceramic particles into Ti and its alloys has proved to be an efficient way to enhance their mechanical and wear properties. Our purpose in this work was to analyze the corrosion, tribocorrosion, mechanical and morphological effects of combining titanium carbide with titanium metal, to create a unique composite via spark plasma sintering technique (SPS). Composites with different mass percentage (1, 5, 10, 15 and 20 wt %) of ceramic phase were produced. The samples of pure Ti and Ti-6Al-4V alloy were also tested, as a reference. These composites were examined for mechanical properties and corrosion resistance in an environment similar to the human body (Ringer’s solution). Open circuit potential (OPC) and anodic polarization measurements were performed. The properties of titanium composites reinforced with micro- and nanocrystalline TiC powders were compared. It was stated that wear properties were significantly improved with increasing amount of TiC in matrix, especially in the case of nanocrystalline reinforcement. In terms of corrosion resistance, the composites showed slightly worse properties compared to pure titanium and Ti-6Al-4V alloy.
The subject of the study concerns the enhancement of corrosion and wear resistance of nitrided 42CrMo4 steel by the formation of zinc phosphate top layer. The present work is aimed at the assessment of the effect of increasing thickness of nitrided layer from approximately 2 µm to 16 µm on the morphology and properties of zinc phosphate coating. XRD analysis showed that along with the increase in the thickness of the nitrides layer, a change in the phase composition was observed. SEM/EDS examination revealed that top layer consists of crystalline zinc phosphate coating. The shape and size of crystals does not significantly depend on a thickness of nitrides layer but corrosion resistance determined by potentiodynamic method in 0.5M NaCl increased with an increase of thickness of a “white layer”. Similarily the wear resistance determined by the 3-cone-roll test was also the highest for 16 µm nitride layer.
The article discusses tests concerning the assessment of the corrosion resistance, properties and the structure of TIG braze welded galvanised steel sheets. Test butt joints were made of 0.9 mm thick galvanised car body steel sheets DC04 (in accordance with EN 10130), using a robotic welding station and a CuSi3Mn1 braze (in accordance with PN-EN 13347:2003) wire having a diameter of 1.0 mm. The research-related tests aimed to optimise braze welding parameters and the width of the brazing gap. The test joints were subjected to visual tests, macro and microscopic metallographic tests, hardness measurements as well as tensile and bend tests. The corrosion resistance of the joints was identified using the galvanostatic method. The tests revealed that it is possible to obtain high quality joints made of galvanised car body steel sheets using the TIG braze welding process, the CuSi3Mn1 braze and a brazing gap, the width of which should be restricted within the range of 0.4 mm to 0.7 mm. In addition, the joints made using the aforesaid parameters are characterised by high mechanical properties. The minimum recommended heat input during process, indispensable for the obtainment of the appropriate spreadability of the weld deposit should be restricted within the range of 50 kJ/mm to 70 kJ/mm. At the same time, the aforesaid heat input ensures the minimum evaporation of zinc. Joints made using the TIG braze welding method are characterised by high resistance to electrochemical corrosion. The galvanostatic tests did not reveal any traces of corrosion in the joint area.
In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was
determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition
after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and
650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings
matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking
time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the
formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings.
Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in
comparison to raw castings, in contrast to the significant increase in mechanical properties.
The Ca50Mg20Zn12Cu18 was assessed with different methods in order to characterize its basic characteristics, and to determine whether the amorphous alloy of such composition would be applicable as an implant material. The XRD analysis was conducted to conclude the structure of the initial material. The Ca50Mg20Zn12Cu18 ingot sample demonstrates crystalline structure containing two main intermetallic phases, however as-cast plates show features of an amorphous material, revealing the characteristic amorphous halo on the x-ray patterns. It was confirmed by the scanning electron microscopy method and fracture images revealing chevron pattern morphology with shell type fracture. Corrosion resistance, was studied using the potentiostatic analysis. The amorphous samples show higher resistance than the crystalline one. Post corrosion surface of the Ca50Mg20Zn12Cu18 alloy exhibits high concentration of magnesium and calcium hydroxides, forming the globular structures in large aggregates of spherical units.
The paper presents the research results of the solenoid housing made of the Zn4Al1Cu alloy that was destroyed as a result of corrosion.
Surface of the tested part showed macroscopically the features typical for white corrosion, and the resulting corrosion changes led to a
disturbance of the alloy cohesion. The research performed have shown that the tested solenoid valve has intergranular corrosion as a
reaction of the environment containing road salt. The corrosion was initiated in the areas of the alfa phase existence appearing in the
eutectic areas which propagated over dendritic areas of the alloy. Initiation of the corrosion followed as a result of the galvanic effect of
the alfa phase reach in aluminium showing higher electrochemical potential, in contact with the eta phase reach in zinc. The impact of the
phase reach in lead present in the microstructure on the corrosion processes run was not found.
Within the presented work, the effect of austenite transformation on abrasive wear as well as on rate and nature of corrosive destruction
of spheroidal Ni-Mn-Cu cast iron was determined. Cast iron contained: 3.1÷3.4 %C, 2.1÷2.3 %Si, 2.3÷3.3 %Mn, 2.3÷2.5 %Cu and
4.8÷9.3 %Ni. At a higher degree of austenite transformation in the alloys with nickel equivalent below 16.0%, abrasive wear resistance
was significantly higher. Examinations of the corrosion resistance were carried out with the use of gravimetric and potentiodynamic
method. It was shown that higher degree of austenite transformation results in significantly higher abrasive wear resistance and slightly
higher corrosion rate, as determined by the gravimetric method. However, results of potentiodynamic examinations showed creation
of a smaller number of deep pinholes, which is a favourable phenomenon from the viewpoint of corrosion resistance.
The oral cavity due to its temperature fluctuations, changing pH, high humidity, action of mechanical forces and the presence of microorganisms is a favorable environment for degradation of dental materials. The paper presents comparative results on orthodontic arch-wires AISI304 steel before and after low temperature plasma nitriding carried out at cathodic potential (conventional) and at plasma potential, i.e. in a process incorporating an active screen. Corrosion resistance test on nitrided layers produced on stainless steel were carried out via electrochemical impedance spectroscopy (EIS) and the potentiodynamic method in non-deaerated artificial saliva solution at 37°C. The results were complemented with analysis of the structure, surface topography and microhardness. The results showed an increase in corrosion resistance of AISI304 steel after conventional glow-discharge nitriding.