The Inhibitive Effect of Cerium Carbonate on the Corrosion of Brass in 3% NaCl Solution

International audienceWe investigated the protective efficiency of a new class of ‘green’ corrosion inhibitors on Copper-Zinc alloy (Brass). The inhibition effect of cerium carbonate (CAC) on Brass in 3% NaCl solution was investigated at room temperature both by potentiodynamic polarisation and impedance spectroscopy (EIS) methods and weight loss measurements. The surface analysis was made by scanning electron microscope and micro-Raman spectroscopy. The electrochemical measurements showed that the CAC decreases the density of the corrosion current and thus acts as a mixed type inhibitor. The CAC inhibits the corrosion of Brass by blocking the active sites of the metal surface with a maximum inhibitory efficiency of 84%, obtained with the concentration of 100 ppm of the inhibitor. The corrosion rate decreased by a factor of 3.5 in the presence of CAC, suggesting that the investigated method is promising. The mechanism of inhibition effect is attributed to adsorption of Ce-hydroxides in the excess of OH-production from the cathodic reactions of water reduction and O2. This hydroxide precipitates subsequently as a barrier against the corrosion of the active regions

Microstructure and crystallographic properties of Cu77Zn21 alloy under the effect of heat treatment

International audienceThe influence of heat treatment process on microstructure and physiochemical properties of Cu77Zn21 alloy was studied. Samples were heated from 300 to 700°C for 15 minutes and gradually cooled to room temperature. Samples were characterized using mechanical testing and surface analysis techniques. It was observed that the grain size increases with the increasing temperature. The decrease in hardness is due to composition change of the Cu-Zn alloy attributed to zinc diffusion.XRD shows the presence of only α brass with a preferential orientation along the (111) plane. The analyses show that temperature affects the crystalline parameters. The rms microstrain was reduced mainly by thermal activation. The heat treatment promotes atomic diffusion and leads to a better crystallinity of the particles. The results of Raman investigations confirmed the changes in the Cu-Zn alloy surface composition with a clear enrichment in CuO. This behavior correlates with the results obtained by mechanical testing. © 2018, © 2018 Informa UK Limited, trading as Taylor and Francis Group

Microstructure and crystallographic properties of Cu77Zn21 alloy under the effect of heat treatment

The influence of heat treatment process on microstructure and physiochemical properties of Cu77Zn21 alloy was studied. Samples were heated from 300 to 700°C for 15 minutes and gradually cooled to room temperature. Samples were characterized using mechanical testing and surface analysis techniques. It was observed that the grain size increases with the increasing temperature. The decrease in hardness is due to composition change of the Cu-Zn alloy attributed to zinc diffusion.XRD shows the presence of only α brass with a preferential orientation along the (111) plane. The analyses show that temperature affects the crystalline parameters. The rms microstrain was reduced mainly by thermal activation. The heat treatment promotes atomic diffusion and leads to a better crystallinity of the particles. The results of Raman investigations confirmed the changes in the Cu-Zn alloy surface composition with a clear enrichment in CuO. This behavior correlates with the results obtained by mechanical testing. © 2018, © 2018 Informa UK Limited, trading as Taylor and Francis Group

Influence of Spray Parameters on the Metallurgical and Functional Properties of HVOF WC Based Cermets Deposited onto Low Alloy Steel

Abstract: Tungsten carbide based spray coatings are widely used in industry for application requiring abrasion, sliding, fretting and erosion corrosion resistance. High velocity oxy-fuel (HVOF) flame spraying was used for producing high quality carbide composite coatings. In this study, a WC-CoCr and WC-CoCrNi powders were thermal sprayed using a HVOF process. The spray parameters were varied in order to investigate their influence on microstructure and mechanical properties of coatings. It is possible to produce homogeneous coating by controlling the flame temperature, the velocity of the gun transverse, the powder feed rate and the nature of the powders. The mechanical properties and the porosity rate could be optimized in order to improve the functional properties

Corrosion behavior in artificial seawater of thermal-sprayed WC-CoCr coatings on mild steel by electrochemical impedance spectroscopy

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Factors influencing corrosion of metal pipes in soils

Deterioration of buried metal pipes due to corrosive soil environment is a major issue worlwide. Although failures of buried pipe due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding factors causing corrosion of buried pipes is necessary. This article reviews factors causing corrosion of buried pipes in soils. Factors include moisture content, soil resistivity, pH, dissolved oxygen, temperature and microbial activity. Moreover, we discuss the influence of manufacturing method and the comparison of corrosion behaviour of cast iron, ductile and mild steel pipes. We found that corrosion rate of pipes increases with moisture contents up to the critical moisture value. Although pH affects corrosion, there is no relationship between corrosion and pH and the corrosion rates of buried pipes are inversely proportional to soil resistivity. Soils containing more organic matter show high resistivity. Dissolved oxygen in soil develops differential cell which accelerates corrosion of metallic pipe. Different types of bacteria present in soil develop biofilms on metallic pipes, which deteriorates pipes with time