Browse

1 - 10 of 167 items :

  • Materials Sciences x
  • Ceramics and Glass x
  • Industrial Chemistry x
Clear All
Corrosion and corrosion inhibition in an environment of ethanol – gasoline blends

Abstract

Ethanol produced from renewable resources is considered as an ecological substitute for a fossil gasoline. Ethanol blended with the fossil gasoline is able to significantly change the properties of the blended fuel as polarity, conductivity, ability to absorb air humidity and ability to dissolve a high percentage of water etc. All these properties are growing with an increasing content of ethanol and all of them can cause higher corrosivity of blended fuel. Material compatibility of metalic construction materials of the vehicle fuel system is also decreased in the environment of ethanol – gasoline blends (EGB’s). Furthermore, components of production, transport and storage equipment may be at risk of corrosion. EGB’s with an ethanol content of about 60% vol. show high corrosive aggressivness, especially if they are contaminated with water and trace amounts of ion, which may occur if proper storage, transport and production conditions are violated. Losses caused by corrosion of equipment may be prevented by using of suitable additive. Diethylenetriamine (DETA) can be used as such additive for the mild steel which is one of the most commonly used construction material. When DETA is used, it shows very high efficiency.

Open access
Corrosion-mechanical behavior of gas main steel in saline soils

Abstract

The study of the deformation behavior of the pipeline material in conditions of loads and influences simulating the operation allows better estimation of the residual life of the pipelines and more accurate forecasting of the operating costs. The kinetics of deformation in 6 model environments simulating soil electrolytes was studied. Corrosion-mechanical tests were performed and the impact of the soil electrolyte chemical composition and the applied mechanical stresses on the corrosion behavior of the pipeline steel was studied. Significant increase in the corrosion activity of the soil electrolyte due to the synergistic effect of the corrosion-active components was found in the specified ratios of the ionic molar concentrations of sulphate and chloride ions (0.05 M: 0.1 M).

Open access
The oxidation kinetics of depleted uranium and its low-alloy molybdenum alloys in moist air

Abstract

The oxidation kinetics of depleted uranium and its low-alloy molybdenum alloys (U-2wt.%Mo, U-5wt.%Mo) were measured in a moist air (75% relative humidity) at 60 and 75 ° C. Coefficients of reaction rate equations were determined for linear oxidation kinetics. In the oxidation of depleted uranium at 75 ° C, a change in reaction kinetics from linear to exponential behaviour was observed after about 2500 hours.

Open access
Static corrosion tests of iron-based biomaterials in the environment of simulated body fluids

Abstract

Biodegradable metallic implants are materials that serve as a temporary implants and scaffolds. They degrade directly in vivo and therefore eliminate need for secondary surgical intervention. They are often made of metals such as magnesium, iron, zinc and can be modified by coating with the inorganic or polymeric layer. In this work iron-based biomaterial was prepared and modified with polymeric (polyethyleneimine, PEI) layer. Its degradation behavior was studied under conditions of simulated body fluids at 37 ± 0.2 °C in the form of static immersion tests. It has been shown that the surface modification caused an acceleration of degradation of the material and also had an influence on the corrosion mechanism.

Open access
Survey and restoration of outdoor glass reinforced polyester sculptures

Abstract

The beginning of the use of polyester resins for artistic work date back to the late 1950s. Initially, resins were supposed to temporarily replace and imitate traditional but more expensive sculptural materials (stone, bronze). Later, original, especially fiberglass works were created, where the laminate formed a shell connected to the internal supporting steel structure. Until now, only part of the exterior works of art made of polyester resins have been survived. Although polyester resins are considered to have good weather resistance, most exterior sculptures exhibit more or less severe defects, often resulting from neglected maintenance. The main types of defects occurring in polyester fiberglass works are presented. The most serious damage is cracks in the entire thickness of the shell, because water can easily penetrate to the internal steel structure. In the case of prolonged water penetration, the statue may collapse due to corrosion. The article presents the procedure of exploring the fiberglass sculpture from the 1950s with the introduction of suitable methods for the documentation of the state of the work. Finally, suitable restoration interventions to maximize the life of the statues are discussed.

Open access
Corrosion behaviour of the titanium beta alloy nanotubular surface in the presence of fluoride ions

Abstract

The titanium bioactivity could be increased by surface nanostructuring. Titanium alloys are using for dental implants manufacturing. It represents a specific problem because of using of the dental treatments with high concentration of fluoride ions and with acidic pH. The corrosion resistance of nanostructured surface of titanium beta alloy in environments with fluoride ions was examined by common electrochemical technique. The electrochemical impedance measurement showed high corrosion resistance in physiological solution. The fluoride ions have expected negative influence on corrosion behaviour of the layer. The nanotube bottom was preferentially attacked which resulted in layer undercoroding and its detachment.

Open access
Corrosion resistance of AZ31 magnesium alloy treated by plasma electrolytic oxidation

Abstract

The coating prepared by plasma electrolytic oxidation (PEO) was created on AZ31 magnesium alloy surface with the aim to evaluate its effect on corrosion resistance. The DC current was applied on the sample in solution consisted of 10 g/l Na3PO4·12H2O and 1 g/l KOH. Additional samples were prepared with 2 and 4 minutes of preparation to observe evolution of the PEO coating. Morphology of the coatings was evaluated by scanning electron microscopy and chemical composition was examined by EDX analysis. Electrochemical characteristic were measured by potentiodynamic polarization tests and electrochemical impedance spectroscopy in 0.1 M NaCl at the laboratory temperature. Obtained data were presented in form of potentiodynamic curves and Nyquist diagrams. Results of analysis showed that plasma electrolytic oxidation coating positively influence corrosion resistance of AZ31 magnesium alloy in chosen corrosive environment.

Open access
Effect of heat treatment on microstructure, microhardness and corrosion resistance of ZE41 Mg alloy

Abstract

Magnesium and its alloys are now attracting a great attention as promising materials for several light weight engineering applications. ZE41 is a new Mg alloy contains Zinc, Zirconium and Rare Earth elements as the important alloying elements and is widely used in aerospace applications. In the present study, heat treatment has been carried out at two different temperatures (300 and 335 °C) to assess the effect of heat treatment on microstructure and corrosion behavior of ZE41 Mg alloy. The grain size was observed as almost similar for the unprocessed and heat treated samples. Decreased amount of secondary phase (MgZn2) was observed after heat treating at 300 °C and increased intermetallic phase (Mg7Zn3) and higher number of twins appeared for the samples heat treated at 335 °C. Microhardness measurements showed increased hardness after heat treating at 300 °C and decreased hardness after heat treating at 335 °C which can be attributed to the presence of higher supersaturated grains after heat treating at 300 °C. The samples heat treated at 335 °C exhibited better corrosion resistance compared to those of base materials and samples heat treated at 300 °C. From the results, it can be understood that the selection of heat treatment temperature is crucial that depends on the requirement i.e. to improve the microhardness or at the loss of microhardness to improve the corrosion resistance of ZE41 Mg alloy.

Open access
Properties of coatings created by HVOF technology using micro-and nano-sized powder

Abstract

The paper focuses on assessment the resistance of hot-sprayed coatings applied by HVOF technology (WC–Co–Cr created using powder of two different grain sizes) against erosive wear by dry-pot wear test in a pin mill at two sample angles. As these coatings are designated for the environment with varying elevated temperatures and often are in contact with the abrasive, the coatings have been subjected to thermal cyclic loading and their erosive resistance has been determined in as-sprayed condition and after the 5th and 10th thermal cycles. The corrosion resistance of coatings was evaluated by linear polarization (Tafel analysis).

Open access
Self-crosslinking acrylic latexes containing nanoparticles ZnO with increased corrosion and chemical resistance of coating

Abstract

The requirements put on coating materials are more and more stringent mainly in the environmental domain, especially as regards VOC emissions. This is why water-based binders as alternatives to solvent-based binders, to provide paints possessing equally good use properties, are intensively sought. The objective of this work was to assess the anticorrosion and chemical properties of paint films based on new self-cross-linking acrylic latexes. The latexes were synthesized via two--step emulsion polymerisation to obtain a core-shell system. Nanostructural ZnO in an amount of 1.5 wt. % was added to the system during the latex binder synthesis. Paints with an enhanced corrosion resistance and chemical resistance of the films were prepared. The binders prepared were pigmented with anticorrosion pigments and their properties were compared to those of commercial water-based dispersions with either identical or different paint film formation mechanisms. The results gave evidence that if a well-selected pigment is used, the binders can be used to obtain anticorrosion coating materials for metallic substrates.

Open access