Papers by Keyword: Corrosion

Abstract: Acrylic coatings were modified by adding 0.5 and 1.0% (v/v) of epoxysilane-treated (aluminosilicate, muscovite, nepheline syenite, and wollastonite) and alkoxysilane-treated (aluminosilicate) mineral fillers. Corrosion behavior of coated carbon steel specimens was studied using polarization method. Wetting behavior and adhesion of specimens were evaluated by static contact angle and cross-cut tape test. Addition of silane-treated mineral fillers dramatically improved the corrosion resistance of acrylic coating, with composite coating filled with alkoxysilane-treated aluminosilicate at 0.5% concentration showing significantly low corrosion tendency and rate in 2 M HCl solution. Contact angle also increased with the addition of fillers, with composite coating containing alkoxysilane-treated aluminosilicate at 0.5% yielding the highest mean value. Adhesion of acrylic coatings was enhanced after addition of fillers at 0.5%, with composite coatings filled with wollastonite and alkoxysilane-treated aluminosilicate giving the lowest percent area removed after application of adhesive tape. Alkoxysilane-treated aluminosilicate was found consistent in improving the anti-corrosion characteristics, water resistance, and adhesion to carbon steel of acrylic coatings.

Abstract: The main point of this paper is to assess the level of corrosion damage of the composite textile fiberglass reinforcement in environments that simulate the concrete pore solution by the techniques of FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) as well as EDS (scanning electron microscopy). Effect of corrosion on the tensile strength segmented textile glass fiber was tested and also it was investigated specific type of protective organic coating on glass fiber. The results express the evidence of local corrosion damage on the examined samples just at pH 13.5, and on the contrary high stability in the environment simulating carbonated concrete and concrete contaminated by chloride anions. The thesis also points on the unevenness of the excluded protective organic coating with localized porosity which relates to the above mentioned corrosion damage.

Abstract: In this article we have used new anticorrosion investigating techniques and studied new polarization resistance aspects of anticorrosion mechanism of cucurbit [n] urils and thioglycolurils based inhibitors in aggressive acid and alkaline containing chloride mediums. Results suggest that the active complex of inhibitor with iron is non-soluble and stable in aggressive mediums.

Abstract: The corrosion of concrete structures is serious in sulfuric acid environments. Corrosion damage of reinforcements caused sulfuric acid corrosion is very serious. The rapid experiments of sulfuric acid corrosion steel bars were carried out, and the apparent morphology and mechanical properties of sulfuric acid corrosion steel bars were studied. The results show that the corrosion of steel bars is uniform corrosion. With the increase of corrosion rate, the yield platforms and the yield strengths and ultimate strengths are reduced. Based on the experimental datas, the relationship models between yield strengths and ultimate strengths and corrosion rates were obtained. The constitutive models of corrosion steel bars were established. The stress - strain relationship model is in good agreement with the experimental data.

Abstract: The scanning electrochemical microscope (SECM) offers a highly sensitive route to evaluate degradation reactions and protection methods with chemical selectivity by using ion-selective microelectrodes as tips, thus operating SECM potentiometrically. Spatially resolved imaging of electrochemical reactivity related to each component of the investigated material can thus be effectively monitored selectively both in situ and in real time. The applicability of this method has been illustrated using a practical example of a metal-coating system, consisting in the exposure of cut edges of coil-coated galvanized steel to aqueous saline environment. In this contribution, localized pH and zinc(II) ion distributions originated around cut edges of coil coated steel immersed in 1 mM NaCl solution are shown.

Abstract: The problematic of pitting corrosion on blades of Kaplan turbine is discussed. Corrosion behaviour was observed during the first year of service. Material of the water turbine blades is martensitic stainless steel GX4CrNi13-4. Chemical composition and hardness of blades was measured, EDS analysis of corrosion products and microstructural evaluation on replicas were carried out. The main problem was found in heterogeneities in the cast microstructure and local disproportions in chemical composition. Influence of microbiologically induced corrosion and surface roughness is considered.

Abstract: The main causes of the damage of a compressor’s turbine blade are documented and described in the article. The turbine blade was made from titanium alloy grade 5 (VT6, Ti-6Al-4V). The analysed segments of the turbine blade were damaged by corrosion and erosion. The sample from the damaged blade was compared with an undamaged reference sample. The observed substantial distinctions between microstructure of the damaged and the reference sample were found using of light and scanning electron microscopy. The observed distinctions of the microstructure were caused by the differences in the heat treatment process.

Abstract: Magnesium and its alloys are considered for application as materials for biodegradable implants as they have mechanical properties similar to bone tissue. High demands on corrosion and mechanical properties are made on these alloys. While mechanical properties of magnesium are usually enhanced by alloying, corrosion properties may deteriorate. This paper is focused on the comparison of magnesium alloys AZ31 (3 wt. % Al, 1 wt. % Zn) and WE43 (4 wt. % Y, 3 wt. % Nd) which are considered for biomedical applications. Besides the type of alloying elements, the preparation process has also great impact on final mechanical and corrosion properties. Alloying elements may be dissolved in magnesium matrix or they can form intermetallic phases, which alter final properties. Microstructure, mechanical and corrosion properties of AZ31 and WE43 were studied and compared with pure magnesium.

Abstract: This contribution deals with the analysis of the failure of a rotating blade of the third wheel (L-1 stage) of the LP rotor of a 200 MW turbine at the power station in Počerady. Material analysis of the blade showed that the cause of the blade fracture was the initiation and growth of a fatigue crack from a corrosion pit. Failures of low-pressure blades have occurred repeatedly on machines of the same design in the power stations of the ČEZ group in recent years and by a similar mechanism. Therefore, based on the knowledge obtained by EPRI (Electric Power Research Institute), ČEZ, a.s. has developed a methodology which can, in real conditions during checks of turbines, reliably detect the parameters of corrosion pits and predict the possibility of development of fatigue damage from these pits. The work summarizes the methodology and the conditions of its use with an emphasis on the fields of its application.

Abstract: A simple chemical conversion coating was adopted to deposit zinc calcium phosphate (ZCP) coating and strontium doped ZCP (SZCP) coating on AZ31 magnesium alloy to induce biocompatibility and reduce the degradation rate. The surface morphology, chemical composition and functional groups of the coating were characterized by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), X-Ray Diffraction (XRD) studies and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy respectively. SZCP coating formed at 20 min deposition time produced crack free surface with a high degree of crystallinity with barrier property, which ultimately retards the dissolution of magnesium in Simulated Body Fluid (SBF). The corrosion resistance of AZ31 magnesium alloy was improved by SZCP coating as evident from hydrogen evolution test (HET). Cytotoxicity evaluation with L969 cells showed that Sr doped ZCP coatings showed less toxicity on resorbable magnesium alloys.