Papers by Keyword: Open Circuit Potential

Abstract: The importance of non harmful inhibitors has informed the application of drugs as an agent to mitigate corrosion of metal materials. This research reveals the inhibitive reaction and adsorption mechanism of Chlorpheniramine drug (CD), on mild steel in an HCl solution using Potentiodynamic polarization, open circuit potential and weight loss method. The CD inhibitor was proportioned into 2.5, 5, 7.5, and 10ml while molarity of HCl was varied in the proportion of 0.1, 0.5, 1.0 and 1.5M at a temperature of 298 K. The reaction showed that as the CD concentration moves to higher concentration, the efficiency of the inhibitor increases, also the higher the concentration of the acid, the higher the corrosion rate. Observation from the result revealed that CD inhibitor protected the steel from corrosion destruction. The optimum efficiency occurred as 85.80% at 10ml CD concentration. CD inhibitor obeyed Freundlich law of isotherm with the average regression value of R² = 0.9733, as R² value gets close to unity. Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectra (EDX) results also confirm strong adsorption mechanisms of CD inhibitor on the mild steel samples. Keywords: Chlorpheniramine Drug; Green Inhibitor; Open circuit potential; Potentiodynamic Polarization; Mild steel

Abstract: This paper presents the results of a study on the effect of geopolymer coating on mild steel. Geopolymer is synthesis of a fly ash and alkaline activators which are sodium hydroxide solution (NaOH) and sodium silicate solution (Na₂SiO₃). Fly ash is one of residue produced during the combustion of coal in coal power plant. In this study, fly ash class F based geopolymer was used as a source material. The alkaline activators then were mixed with fly ash to produce the geopolymer paste which acts as a coating material. The mixture was placed in molds and reinforcement bar were embedded in geopolymer paste. After that, the corrosion behavior of reinforcement bars for all samples were observed by using Open Circuit Potential (OCP) testing. Referring the pourbaix diagram regarding OCP testing, samples are in passivity region. Besides that, mild steel also were coated with geopolymer paste for adhesion test. Elcometer 108 was used for adhesion strength test. Morphology analysis also been used to determine the microstructure of fly ash and geopolymer paste. Phase analysis was used for the analysis phase between fly ash, geopolymer paste and mild steel coated with geopolymer paste. From OCP test, pourbaix diagram shows that samples is placed in the passivity region, iron (III) oxide (Fe₂O₃) which is in stable phase and iron (II, III) oxide same results as in phase analysis. The minimum potential value for OCP is 0.015 V and the maximum potential value is 0.133 V. For adhesion strength, day 14 got the highest results compared day 7 and day 3 which the results are 2.0 Mpa, 1.9 Mpa and 1.5 Mpa respectively. It is because from day 3 until day 14, the structure of geopolymer paste becomes more compact, denser and better crystallization as shown in morphological analysis.

Abstract: Electrochemical impedance spectroscopy (EIS) is a technology of nondestructive electrochemical testing. In this paper, EIS is applied to study the corrosion processes of Al-Mg coatings. In the initial 24 h of immersion in 3.5% NaCl solution, passive films of Al-Mg coatings dissolve quickly. As time passed, corrosion products increase on surface gradually, which can inhibit corrosion. After 480h of immersion, corrosion products fully cover on Al-Mg coatings’ surface. The EIS of different corrosion processes are fitted by three equivalent circuits corresponding to the three corrosion processes. In the test of open circuit potentials (OCP), OCP is instable in the initial 24 h of immersion. As immersion time goes by, OCP tends to stabilization at about -0.90 V. Measurements of scanning electron microscope (SEM) confirm the conclusions of electrochemical measurements.

Abstract: This study deals with the evaluation of self-healing ability of conducting polymer corresponding to a corrosion process. Poly ortho-anisidine (PoA) was doped with Phosphomolybdic acid (PMA) and Tungstosilicic acid (TSA) and incorporated in polyvinyl butyral (PVB) coatings. The self-healing abilities of coatings were evaluated using open circuit potential (OCP) in 0.1 M NaCl solution for 45 hours of immersion. The coatings containing doped PoA showed increased positive potential of OCP after 45 hours of immersion as compare toblank PVB which showed a constant profile of OCP over the time indicating uniform corrosion under the coating.Thermogravimetric analysis (TGA) showed that PoA doped with TSA is more stable and more effective in the coating. High resolution Transmission Electron microscopy (HR-TEM) and Energy dispersive x-ray spectroscopy (EDX) confirms the doping of PoA.

Abstract: The paper discusses the electrochemical interactions of Co-Cr alloy with different physiological solutions and organic substances, containing different ions and different pH values, which should play a key role in the materials lifetime. The physical and chemical reactions are numerous and the passivity of the Co-Cr alloy is submitted to the influence of the liquid environment. Some electrochemical investigations were carried out for understanding and predicting the passivity and the corrosion resistance of Co-Cr alloy in three types of simulated body fluids (SBF), namely Fusayama Meyer artificial saliva (pH=5), Hank’s solution (pH=7.4), Ringer's solution (pH=6.6) and citric acid as organic solution. The reason of using another type of environment (other than SBF), such as citric acid is that this medium is a powerful oxidant and has a lower pH value (pH=1.8). This acid environment can influence the state (the formation and growth) of the oxide layer on the surface of the alloy. Research has shown different behavior of the cobalt chromium alloy according to the pH, the chloride content and the oxidizing nature of the environment. Co-Cr alloy biomaterial, immersed in four aqueous media reveals that there are different levels of stabilization of the potential and different current densities depending on the pH value. The Co-Cr alloy biomaterial is very sensitive to localized corrosion (pitting) in Hank solution.

Abstract: Metallic biomaterial are the most suitable for replacing failed hard tissue up to now and for that is important to know the tribocorrosion resistance of these materials before use in biomedical applications. Surface engineering can play a significant role in extending the performance of medical implants made of titanium and its alloys. In this work was chosen electrodeposition of hydroxyapatite (HA) coatings into nanoporous titania layer formed by anodic oxidation as modified Ti-6Al-4V alloy surface. The comparative tribocorrosion behavior of untreated Ti-6Al-4V alloy surface, anodic nanoporous TiO₂ surface and electrodeposited hydroxyapatite (HA) coatings into nanoporous TiO₂ layers has been investigated in a bio-simulated fluid solution. The results of these investigations have shown that both surface treatments applied have improved the tribocorrosion resistance and friction coefficients as compared to the untreated Ti–6Al–4V alloy surface.

Abstract: This paper presents an experimental study on corrosion of carbon steel as reinforcement bar in artificial solution of geopolymer paste by Open Circuit Potential (OCP). The OCP measurements have been used in reinforcement bar concrete studies for many years to determine the corrosion behavior of materials. OCP is the potential of the working electrode relative to the reference electrode when no current or potential is being applied to cell. The OCP of reinforcement bar was recorded with time and this experiment has been done for 30 days. A copper/copper sulfate (Cu/CuSO₄) reference electrode with a potential V-SHE of +0.318 V (at 25oC) was used in this study. The pH of geopolymer concrete was observed to be in the range of 11.5 to 12.5 depending on the formulations. Thus, in this study the artificial solutions of geopolymer paste that were used are pH 11, pH 12 and pH 13. It has been found that the potential values of three solutions were fluctuated from the beginning until day 30. The highest potential value was indicated by pH 13 whereas the maximum value is 0.542 V and minimum value is 0.205 V while pH 11 shows the lowest potential value with the maximum value 0.356 V and the minimum value-0.047 V. However, all the redox potential values for pH 11, pH 12 and pH 13 were located at passivity region, Fe₂O₃. The Fe₂O₃ is the stable phase in which this oxide acts as a protective film or passive layer in this region. It would be expected to provide some protection against corrosion. Keywords: corrosion, artificial solution, geopolymer paste, reinforcement bar, open circuit potential, passivity

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: This objective is to study the influence of pH on the electrochemical behavior of 00Cr15Ni7Mo2Cu2 supermartensitic stainless steel in 3.5% NaCl solutions using potentiondynamic polarization technique, open circuit potential tests and electrochemical impedance spectroscopy (EIS).The study reveals that the pitting potential (Eb) is higher, the passivation current densities (ip) is lower and the electrochemical impedance increases with the pH. The results indicate that this stainless steel offer good pitting corrosion resistance with the pH increasing in 3.5% NaCl solutions.

Abstract: The marine corrosion of aluminium alloys, AA1100 and AA6061 was investigated in term of the transient of the open circuit potential and polarization behaviors in a simulated marine condition. The pitting potential increased with dilution ratios of artificial seawater. The aluminium alloys passivated at lower potentials in the relatively concentrated solutions. The open circuit potential reached the passive state faster at lower solution temperature than that in higher solution temperature. The pitting potential of AA1100 and AA6061 seems independent of the test solution temperature, and the difference between pitting potential and the corrosion potential became smaller at the lower solution temperature. The involvement of the sulfate compound resulted in the increase in pitting potential and had no effects on the passive current density. The absence of the sulfate ions slowed down the formation rate of the passive film. Especially, the open circuit potential of AA6061 passivated at lower potential due to the absence of the sulfate ions.