Search results

The purpose of this paper is to study the cause of severe corrosion of the galvanized lightning rods in a 220 kV transformer substation, and to seek the effective corrosion inhibition measures for the hollow lightning rods.

The corrosion morphology and rust component of lightning rod was analyzed, and the corrosion process of lightning rod was researched by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), ion chromatography and electrochemical tests.

The results indicated that the outer surface of hollow lightning rod was corroded slightly; however, its inner surface suffered severe corrosion because of a long time high-humidity environment inside the tube caused by the rainwater permeation. A rust layer consisted of Fe₃O₄ and a little FeOOH was accumulated on the inner surface of the hollow lightning rod. Moreover, Fe₃O₄ rust layer worked as a large cathode area which could promote the corrosion of metal substrate further. A self-accelerating corrosion process was formed on the inner surface, making the corrosion failure of lightning rod occurred and aggravated gradually.

The corrosion of inner surface of hollow lightning rod cannot be detected easily. More attention should be paid to the corrosion inhibition of lightning rod. The key of corrosion inhibition for the hollow lightning rod was to avoid the rainwater accumulation inside tube. The research results can provide guidelines on the corrosion inhibition measures selection of lightning rod in transformer substation.

The purpose of this paper was to study the corrosion control of B10 copper-nickel alloy using the LiOH-N₂H₄ compound inhibitors and to evaluate the feasibility of replacing the original inhibitors (NaNO₂-Na₂MoO₄) with the new ones (LiOH-N₂H₄) for the chilled water system in a nuclear unit.

The corrosion resistance performance of B10 copper-nickel alloy was evaluated during the whole replacement process of inhibiters using electrochemical tests and surface analysis techniques.

The results indicated that the corrosion of B10 copper-nickel alloy could be prevented effectively using LiOH to increase the pH value of solution higher than 10.0 and using N₂H₄ to consume dissolved oxygen. During the replacement process of inhibitors from NaNO₂-Na₂MoO₄ to LiOH-N₂H₄, the corrosion resistance performance of B10 copper-nickel alloy had not decreased greatly. The new LiOH-N₂H₄ inhibitor, which could enhance the compactness of rust, was able to reduce the corrosion rate of rusted B10 metal.

It is feasible and operable to replace the NaNO₂-Na₂MoO₄ inhibitors with the LiOH-N₂H₄ inhibitors for the corrosion prevention of B10 copper-nickel alloy. The research results can provide guidelines for the inhibitor selection of chilled water system in a nuclear unit.

The purpose of this investigation was to study the effects of sodium hexametaphosphate and zinc sulfate on the corrosion control of rusted iron in reverse osmosis (RO) product water of seawater.

The synergistic effects and inhibition effects of corrosion inhibitors on rusted carbon steel were studied using the weight-loss method, electrochemical tests and surface analysis techniques.

The results indicated that sodium hexametaphosphate could partly suppress the corrosion of rusted steel, but zinc sulfate used alone had no inhibition effect. Hexametaphosphate and zinc sulfate showed a strong synergistic effect and the optimal ratio of two chemicals was 1:1. The inhibition efficiency appeared to increase with increasing inhibitor concentration and the ideal dosage of inhibitors was set at 20 mg/L, when chemical cost and inhibition efficiency were taken into account. Surface analysis results proved that this compound inhibitor could make the rust layer much more compact. The inhibitive mechanism was to combine with rust and form a protective film, which consisted of iron oxide, polyphosphate and Zn(OH)₂.

It was found that the compound inhibitor consisting of sodium hexametaphosphate and zinc sulfate had a good inhibitive effect on rusted iron in RO product water. The research results can provide theoretical guidelines for corrosion control of rusted pipes in power plants.

The purpose of this study was to investigate the corrosion of rusted carbon steel in dilute NaCl solution, with the purpose of exploring the effect of the rust layer on metal corrosion and establishing a corrosion model for rusted iron.

The corrosion behavior of rusted carbon steel in dilute NaCl solution was studied by means of weight-loss determinations, scanning electron microscopy, Raman spectrometry and electrochemical techniques.

The results indicated that carbon steel had a similar corrosion behavior in all three NaCl solutions. The iron rust, which consisted of a thin γ-FeOOH layer and a thick Fe₃O₄ layer, can facilitate the corrosion process of carbon steel via reduction of γ-FeOOH and the large area cathode of Fe₃O₄. Hence, the corrosion rate of carbon steel was accelerated significantly and finally was determined by the limiting diffusion rate of oxygen.

A corrosion model of rusted carbon steel was established, suggesting that iron rust formed in all slightly acidic waters with low alkalinity probably promotes the corrosion of carbon steel. Anti-corrosion measures for iron in this type of solution, such as desalination water, should be aimed to reduce the promotional effect of the rust layer on metal corrosion.

The purpose of this paper is to explore the long‐term corrosion behavior of carbon steel in 3% NaCl solution and evaluate the effect of rust layer on the corrosion process.

The corrosion behavior of rusted carbon steel in 3% NaCl solution was studied by means of infrared spectroscopy (IR) and electrochemical impedance spectroscopy (EIS).

The results indicated that the corrosion of carbon steel was affected by chloride ion in initial immersion and then controlled by the rust layer. The rust layer consisted of a thin outer layer (γ‐FeOOH layer) and a thick inner layer (Fe₃O₄ layer). The outer rust layer facilitated the cathodic process via reduction of γ‐FeOOH, while the inner rust layer provided a large cathode area and oxygen could be reduced on its surface. As a result, the corrosion rate of carbon steel was determined by the limiting diffusion rate of oxygen and stabilized at a high value.

The corrosion model of rusted carbon steel in 3% NaCl solution was established. It is probable that the iron rust in all slightly acidic water with low alkalinity can promote the corrosion process via reduction of γ‐FeOOH. Anti‐corrosion measures for iron in this type of solutions should be aimed to reduce the promoting effect of rust layer on the metal corrosion. The NaCl solution prepared from tap water is more suitable for the substitution of artificial water than that prepared from deionized water.

Some power plants in China that adopt reverse osmosis (RO) product water as their fresh water source face serious metal corrosion of their water distribution system. The corrosion process of carbon steel in RO product water is still not clear and there is no suitable anti‐corrosion method for the power plant to employ. The purpose of this paper is to study the corrosion behavior of carbon steel in RO product water, determine the factors leading to the high corrosion rate of carbon steel, and then suggest appropriate anti‐corrosion measures.

By measuring polarization curves and AC impedance values of the corrosion system and analyzing corrosion products using scanning electron microscopy (SEM), infrared spectroscopy (IR) and X‐ray diffraction (XRD), the corrosion behavior of Q235A carbon steel in the RO product water derived from seawater was studied.

The experimental results showed that the corrosion process of carbon steel in RO product water is controlled by the diffusion process of oxygen, and the corrosion products contain γ‐FeOOH, Fe₃O₄ and small amounts of α‐FeOOH. Although rust formed had a double layer structure, the outer rust layer, which contained γ‐FeOOH and a little α‐FeOOH, was thin. The inner rust layer, containing Fe₃O₄, was the main component of the rust layer. Due to the weak acidity of RO product water, γ‐FeOOH can be transformed to Fe₃O₄ very quickly and Fe₃O₄ will accumulate on the metal surface. Because of the electrical conductivity and fractured surface of the Fe₃O₄ layer, the corrosion product layer cannot inhibit the corrosion process by hindering the diffusion process of oxygen, and hence the corrosion rate of carbon steel is always high.

The paper describes the first systematic research to be carried out on the corrosion behavior of carbon steel in RO product water. It was found that the generation and accumulation of Fe₃O₄ on the metal surface was the primary reason leading to the high corrosion rate of carbon steel, and anti‐corrosion measures can be chosen following the following rules: deoxygenation, raising of the pH of the solution, or addition of corrosion inhibitors to the solution.

The purpose of this paper is to set out a study of the film‐forming characteristics of octadecylamine (ODA), estimate the feasibility of shutdown protection using ODA at high temperatures, and determine the optimum process condition of shutdown protection for units under full load if ODA has a good film‐forming effect at high temperatures.

An autoclave was used to simulate the water‐vapor environments at 350‐560°C in the water‐steam system of power plants. The decomposition test of ODA was investigated and the ODA film‐forming characteristics were studied for furnace tube materials used in gas‐fired power plants.

Results showed that ODA had a decomposition equilibrium and the decomposition products did not contain harmful organic substances such as low molecular organic acids. ODA would form a satisfactory protective film in the range of 350‐560°C with the best film at 480°C. The protection effect of the film formed by ODA at 560°C was much stronger than was that of its oxide film, which showed the feasibility of shutdown protection using ODA for gas‐fired power plants operating under full load. The optimal conditions of shutdown protection under full load were as follows: the temperature was 560°C, the concentration of ODA was 80 mg/L, the pH was 9.5 and the exposure time was 2 h. From the experimental results of X‐ray photoelectron spectroscopy, it was known that the surface film on the specimens was composed of a compound of ferroferric oxide and ODA, and the film‐forming mechanism was chemical adsorption between N in the ODA and Fe.

It was found that ODA has a good film‐forming effect at high temperatures and it is practicable to implement shutdown protection for base‐load units. The research results can provide theoretical guidelines for shutdown protection of gas‐fired power plants.

The purpose of this paper is to present a sliding mode attitude controller for reusable launch vehicle (RLV) which is nonlinear, coupling, and includes uncertain parameters and external disturbances.

A smooth second-order nonsingular terminal sliding mode (NTSM) controller is proposed for RLV in reentry phase. First, a NTSM manifold is proposed for finite-time convergence. Then a smooth second sliding mode controller is designed to establish the sliding mode. An observer is utilized to estimate the lumped disturbance and the estimation result is used for feedforward compensation in the controller.

It is mathematically proved that the proposed sliding mode technique makes the attitude tracking errors converge to zero in finite time and the convergence time is estimated. Simulations are made for RLV through the assumption that aerodynamic parameters and atmospheric density are perturbed. Simulation results demonstrate that the proposed control strategy is effective, leading to promising performance and robustness.

By the proposed controller, the second-order sliding mode is established. The attitude tracking error converges to zero in a finite time. Meanwhile, the chattering is alleviated and a smooth control input is obtained.

This study aims to identify senior citizens’ requirements related to “embedded retirement facilities (ERFs)”, which are small-scale, multi-functional and community-based care facilities for senior citizens in mainland China, and to discuss whether senior citizens’ perceptions are influenced by their backgrounds.

A questionnaire type of research was administrated to gain senior citizens’ rankings of services that should be provided by ERFs. Non-parametric statistical models were applied to analyse the collected data.

Results reveal that health care services for senior citizens are considered the most important. Requirements regarding rehabilitation and entertainment and daily life assistance are ranked second and third, respectively. Culture-related activities are the least important. Differences in the senior citizens’ background also influence their choices.

This research is based on a questionnaire survey completed in northeast China. Opinions from other areas of mainland China will be collected in the future study. Furthermore, the key items identified in this research, which was completed by participants from the built environment discipline, can be further elaborated by combining interdisciplinary feedback.

This study explores services that are supposedly provided by ERFs. Findings will provide useful perceptions from senior citizens and will enable decision makers to prioritise services for senior citizens.

Although senior citizens are the end users of ERFs, their needs are easily overlooked. This study calls attention to their needs from ERFs, and the results are likely to serve as references for stakeholders in building improved facilities.

ERFs have been provided in mainland China to cater to senior citizens’ needs since 2014. However, few studies have identified senior citizens’ requirements for provided services. The survey-based results of this work will serve as references for various stakeholders in making enhanced decisions.