Papers by Keyword: Electrochemical Measurement

Abstract: This study investigated the electrochemical behavior of Ni–Cu alloy plating baths during plating and dealloying reactions. Furthermore, the potential and plating time effects on the shape of three-dimensional structural Ni–Cu alloy plating film and its adhesion to epoxy resin were investigated. Nodules were observed on the surface of the plating film generated at potentials from-0.5 V to-1.0 V. When the plating films formed at potentials of-1.0 V to-1.5 V were dealloyed, the formation of pores was observed. The shear test results showed that the average shear strength of the specimen joined with epoxy resin between two Cu plates with Ni–Cu alloy plating film formed at a potential of-1.0 V was the highest under all conditions.

Abstract: Electrodeposited Ni-11 mass%P alloy plating film was fabricated on the surface of stainless steel SUS304 to conduct brazing of SUS304 plates for a heat exchanger. Brazing of SUS304 plates with electrodeposited Ni-11P layers was carried out using a hydrogen reducing furnace. The microstructure and joint strength of the brazed joint were also investigated. From the result of the microstructural observation of the cross section of the joint, it was found that the brazing filler metal is homogeneously distributed without defects such as voids between the SUS304 plates. The results of electrochemical measurements showed that the P-concentrated phase in the Ni-11P alloy is preferentially dissolved in NaCl aqueous solution.

Abstract: In order to understand the influence of the tensile stress on the corrosion of reinforcement bars in civil engineering, the reinforcement bars specimens were put into the liquid corrosion tank made of hydrochloric acid and distilled water by applying the tension stress on the reinforcing frame to carry out rapid corrosion. The corrosion of reinforcement bars under different tension stresses was tested by using electrochemical polarization method. The metallographic examination of reinforcement bars was carried out through the section of reinforcement bars. The corrosion mechanism of the stressed reinforcement bar was tested and analyzed. It can be known from the experimental study: First in the same corrosion condition, the larger the tensile stress is, the faster the corrosion of steel bar will be; Second corrosion current density or corrosion rate are index for evaluating corrosion rate of reinforcement bars with different tensile stresses. Corrosion potential can not be used as an index for evaluating corrosion rate of reinforcement bars with different tensile stresses; Third intercrystalline corrosion occurs inside the reinforcement bar due to micro-defects after rolling and moulding, which directly affects the mechanical properties of reinforcement bar.

Abstract: Titanium is not only the most widely used biomaterial for medical implants, but with its very good mechanical properties, corrosion resistance and low density is also applicated in many sectors of industry (aerospace, military, aviation, machinery, energetics, chemicals, etc.). In this paper it is described the influence of temperature on the electrochemical characteristics of Ti-6Al-4V alloy. The surface was mechanically grinded and polished by chemical-mechanical process. Basic electrochemical characteristics were determined by potentiodynamic tests in 0.1M NaCl solution at different temperatures. The obtained results were analysed by the Tafel-extrapolation method. Finally, a modified Arrhenius relation was used for determination of activation energy. The activation energy of grinded and chemical-mechanical polished surface is nearly three times higher than activation energy of only grinded surface.

Abstract: Combining use electrochemical measurement and weight loss testing, the inhibition efficiency of an organic inhibitor was studied in a chloride contaminated solution. The results showed that the added inhibitor can enhance the corrosion potential and decreased the corrosion current density of rebar. The weight loss testing confirmed that the inhibitor reduced the corrosion rate of rebar by 80% in the chloride containing solution. Moreover, the linear polarization results are consistent with the weight loss testing, which suggests that the former is an effective method to estimate the inhibition efficiency of inhibitors.

Abstract: Since Fe-Cu-C sintered steels are easily rusted, they are coated with rust preventive oils. High viscosity of those rust preventive oils decrease workability, and low viscosity deteriorates rust preventive performance. Therefore, it is necessary to develop new rust preventive oils with contradictory properties of low viscosity and superior rust prevention. However, precise methodology to evaluate rust prevention ability has not been established. In this study, we developed new technique to quantitatively evaluate rust prevention ability by measuring the open circuit potential through thin corrosive solution on Fe-Cu-C sintered steels coated with a rust preventive oils. As a result, the ability for rust prevention can be measured quantitatively, and it decreases slowly over time, with repeating destruction and restoration. Furthermore, it was found that the deteriorating processes of rust prevention ability for rust prevention oils are composed of three characteristics steps respectively. That is, in the first step the great open circuit potential changes from 0V to-0.3V with repetition were observed where the excellent rust prevention ability was kept, in the second step it decreases slowly from-0.1V to-0.4V with oscillation of the small potential changes where the gradual decrease of rust prevention ability was recognized and in the third step it decreases monotonously in the lower potential than-0.4V where the rust was observed because of the remarkable deteriorating of the rust prevention ability.

Abstract: New waterborne Al-Zn-Si-RE coatings with improved corrosion resistance were introduced in this study. The corrosion resistance of Al-Zn-Si-RE coatings was evaluated by electrochemical measurements and salt spray test. Evolution of microstructure and phase composition at different exposure time in salt spray test was investigated by scanning electron microscopy and X-ray diffraction technique. The results indicate that Al-Zn-Si-RE coatings provide effective sacrificial protection to the steel substrate but exhibit lower corrosion rate and higher corrosion resistance compared to zinc aluminum coatings. The dense continuous corrosion layer formed on Al-Zn-Si-RE coating acts as a barrier layer, limiting the transport of aggressive species towards the coating-substrate interface and the corrosion rate of the coating; Zinc aluminum hydroxy carbonates are the dominant components in the corrosion layer of Al-Zn-Si-RE coatings.

Abstract: Intergranular corrosion behavior of 00Cr12 ferritic stainless steels with different amounts cerium was evaluated. For this evaluation, electrochemical measurements - polarization curves - were obtained for tested materials, and optical microscope was used to observe corrosive microstructure. Experimental results shows: cerium reduces grain sizes and improves intergranular corrosion resistance of test materials. Through mechanism analysis: cerium reduces grain sizes, increases grain boundary density, therefore might improve distribution aspects of carbides and nitrides, chromium depletion situation near grain boundary would be improved, this work worth further study.

Abstract: Methionine (MET) as a corrosion inhibitor for brass in O2-free 1M NaOH solution was investigated using weight loss, polarization curves, electrochemical impedance spectroscopy(EIS). The surface morphology after corrosion test was observed by scanning electron microscopy (SEM). Results indicate that MET is a cathodic inhibitor, and the inhibition efficiency increases with MET concentration.

Abstract: The inhibiting behavior of 1-ethyl-3-butylbenzotriazolium ionic liquids，[C₂Bt][Br] ,on mild steel corrosion in 5 wt.% HCl as corroding solution was investigated using weight loss，potentiodynamic polarization and electrochemical impedance measurements. The obtained results indicated that [C₂Bt][Br] is a good inhibitor for the mild steel in 5 wt.% HCl solution. The inhibition efficiency increased with an increase of inhibitive concentration. Potentiodynamic polarization data indicated that the [C₂Bt][Br] acted essentially as a mixed-type inhibitor. The electrochemical impedance study showed that corrosion inhibition took place by adsorption.