Abstract:This paper presents the effects of the concentration, temperature, pH and Li 2 CrO 4 on copper corrosion in a concentrated LiNO 3 solution. The LiNO 3 concentration had opposite effects on the copper corrosion. The corrosion rate increased with increasing temperatures, but decreased with increasing pH levels. Below 220 °C, Li 2 CrO 4 promoted the formation of a thin and compact passive film comprising CuO, Cu 2 O and Cr 2 O 3 , which effectively inhibited the copper corrosion. Regarding corrosivity, the maximu… Show more
“…Figure 2(a) shows that copper immersed in S 1 solution got the more active potential during the first seconds (from 0 to 1000 s) with a E OCP of −310 ± 16 mV, decreasing gradually until −320 ± 10 mV. In the presence of LiNO 3 (S 2 solution), E OCP of copper is displaced to less active potentials, registering a value of −245 ± 14 mV shifted throughout the time toward more active potential (−263 ± 9 mV), suggesting the formation of a layer of corrosion products, compounded by CuO and Cu 2 O [14–16] due to the presence of normalNnormalO3− [17] and copper oxidation in Cu + and Cu −2 ion promoting due that the normalNnormalO3−act as a cathodic reagent that produces normalNnormalO2− via: Then the NO2− is converted into nitrous oxide and oxygen ions as it was described by Rizvi et al as follows [18]: The latter allowed the formation of a stable passive film of CuO and Cu(OH) 2 . Figure 2 OCP behaviour for the copper immersed in S 1 , S 2 , S3 and S 4 solutions at 25, 50 and 80°C.…”
Section: Resultsmentioning
confidence: 99%
“…Subsequently, to achieve a more uniform surface, the samples were ground prior to every electrochemical analysis. Four electrolytic solutions were established to evaluate the corrosion effect of the copper immersed in lithium bromide water solution combined with other refrigerant absorbents, the concentrations used were based on the reported by [14] (Table 1).…”
Section: Experimental Methodologymentioning
confidence: 99%
“…Figure 2(a) shows that copper immersed in S 1 solution got the more active potential during the first seconds (from 0 to 1000 s) with a E OCP of −310 ± 16 mV, decreasing gradually until −320 ± 10 mV. In the presence of LiNO 3 (S 2 solution), E OCP of copper is displaced to less active potentials, registering a value of −245 ± 14 mV shifted throughout the time toward more active potential (−263 ± 9 mV), suggesting the formation of a layer of corrosion products, compounded by CuO and Cu 2 O [14][15][16] due to the presence of NO − 3 [17] and copper oxidation in Cu + and Cu −2 ion promoting due that the NO − 3 act as a cathodic reagent that produces NO − 2 via:…”
The present research was focused on analyzing the corrosion resistance of copper in the presence of refrigerant-absorbent combinations such as lithium bromide (LiBr), lithium nitrate (LiNO 3 ) and calcium chloride (CaCl 2 ), used in Adsorption Refrigeration Systems (ARS). Electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, electrochemical noise analyses and potentiodynamic polarisation curves were applied to study the test solution combination effect on the corrosion rate of copper as a structural material in ARS. OCP analyses reveal that the E corr shifted based on the temperature and test solution. Meanwhile, when the copper was immersed in LiBr/H 2 O + CaCl 2 at 80°C, the corrosion current density (I corr ) was lower (0.003 mA/cm 2 ). Also, The R p estimated from EIS shows an increase at 80°C. Micrographs of the copper surface immersed in LiBr/H 2 O and LiBr + CaCl 2 observed cracks and pits. But also, when the corrosion product layer was removed, a less heterogeneous surface was revealed.
“…Figure 2(a) shows that copper immersed in S 1 solution got the more active potential during the first seconds (from 0 to 1000 s) with a E OCP of −310 ± 16 mV, decreasing gradually until −320 ± 10 mV. In the presence of LiNO 3 (S 2 solution), E OCP of copper is displaced to less active potentials, registering a value of −245 ± 14 mV shifted throughout the time toward more active potential (−263 ± 9 mV), suggesting the formation of a layer of corrosion products, compounded by CuO and Cu 2 O [14–16] due to the presence of normalNnormalO3− [17] and copper oxidation in Cu + and Cu −2 ion promoting due that the normalNnormalO3−act as a cathodic reagent that produces normalNnormalO2− via: Then the NO2− is converted into nitrous oxide and oxygen ions as it was described by Rizvi et al as follows [18]: The latter allowed the formation of a stable passive film of CuO and Cu(OH) 2 . Figure 2 OCP behaviour for the copper immersed in S 1 , S 2 , S3 and S 4 solutions at 25, 50 and 80°C.…”
Section: Resultsmentioning
confidence: 99%
“…Subsequently, to achieve a more uniform surface, the samples were ground prior to every electrochemical analysis. Four electrolytic solutions were established to evaluate the corrosion effect of the copper immersed in lithium bromide water solution combined with other refrigerant absorbents, the concentrations used were based on the reported by [14] (Table 1).…”
Section: Experimental Methodologymentioning
confidence: 99%
“…Figure 2(a) shows that copper immersed in S 1 solution got the more active potential during the first seconds (from 0 to 1000 s) with a E OCP of −310 ± 16 mV, decreasing gradually until −320 ± 10 mV. In the presence of LiNO 3 (S 2 solution), E OCP of copper is displaced to less active potentials, registering a value of −245 ± 14 mV shifted throughout the time toward more active potential (−263 ± 9 mV), suggesting the formation of a layer of corrosion products, compounded by CuO and Cu 2 O [14][15][16] due to the presence of NO − 3 [17] and copper oxidation in Cu + and Cu −2 ion promoting due that the NO − 3 act as a cathodic reagent that produces NO − 2 via:…”
The present research was focused on analyzing the corrosion resistance of copper in the presence of refrigerant-absorbent combinations such as lithium bromide (LiBr), lithium nitrate (LiNO 3 ) and calcium chloride (CaCl 2 ), used in Adsorption Refrigeration Systems (ARS). Electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, electrochemical noise analyses and potentiodynamic polarisation curves were applied to study the test solution combination effect on the corrosion rate of copper as a structural material in ARS. OCP analyses reveal that the E corr shifted based on the temperature and test solution. Meanwhile, when the copper was immersed in LiBr/H 2 O + CaCl 2 at 80°C, the corrosion current density (I corr ) was lower (0.003 mA/cm 2 ). Also, The R p estimated from EIS shows an increase at 80°C. Micrographs of the copper surface immersed in LiBr/H 2 O and LiBr + CaCl 2 observed cracks and pits. But also, when the corrosion product layer was removed, a less heterogeneous surface was revealed.
“…Because the steel surface is exposed to air and moisture, the iron in the surface undergoes electrochemical reactions to produce Fe(OH) 2. This will then be further oxidized to Fe2O3 and Fe3O4, and α-FeOOH [25]. After surface preparation, Fe2O3 and Fe3O4 immediately form a thin film on the carbon steel surface which was seen in the obtained XRD pattern.…”
Corrosion of steel structures is one of the main causes of destruction and loss of materials due to the damages it can bring to operating, storage, and structural equipment. Anti-corrosion inhibitors available in the market frequently contain chromium and lead, which are hazardous to human health and the environment. This study focused on the synthesis of nanosilica from the agro-industrial byproduct rice hull ash (RHA) and examined its potential as a corrosion barrier. Steel specimens were prepared in the form of 4mm thick disks cut from 16mm steel bars. RHA nanosilica was synthesized via acid precipitation method and characterized using x-ray diffraction (XRD), dynamic light scattering (DLS), atomic force microscopy (AFM), and Fourier Transform Infrared (FTIR) Spectroscopy. After characterization, 2.5%w/v RHA nanosilica was used to formulate sodium silicate as a coating for the steel specimens. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20Hz to 20MHz frequency range. The generated Nyquist plot showed that the specimen coated with sodium silicate with RHA nanosilica has a much larger diameter than red oxide indicating better protection against corrosion. The generated Bode plots confirmed this result as it showed that the specimens coated with sodium silicate with RHA nanosilica had higher impedances than those coated with red oxide, especially in the low-frequency regions.
“…It has been shown that in water/lithium bromide absorption heat pump systems, corrosion can be a problem especially in the high‐temperature regions of the system and therefore, a careful choice of materials is needed . With common materials such as carbon and stainless steel, ammonia/lithium nitrate solutions have reasonably low corrosion rates at temperatures of up to 150°C …”
Summary
The modeled operating characteristics of a single‐effect ammonia/lithium nitrate absorption heat pump‐transformer (type III absorption heat pump) are presented and compared to other working pair options and absorption heat pump cycles. Heat and mass balance equations are given. The effect of cycle operating parameters is shown on cycle thermal efficiency and solution pump power. It is shown that the ammonia/lithium nitrate working pair would achieve a performance a little less efficient than a water/lithium bromide system. Ratios of useful heat delivered to driving heat of nearly 2 are shown, with this system, to be achievable over a wide range of operating conditions. Ammonia/lithium nitrate has practical advantages over water lithium bromide in relation to corrosion, construction materials, and operating pressures. Both working mixtures have high viscosities in the absorbent/refrigerant solutions. However, an ammonia/lithium nitrate system has much higher available pressure drops for the economizer allowing the designer greater leeway in the use of enhanced heat exchange techniques. Costs and payback are commented upon.
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