scholarly journals Potentiometric Response of Ag/AgCl Chloride Sensors in Model Alkaline Medium

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Farhad Pargar ◽  
Hristo Kolev ◽  
Dessi A. Koleva ◽  
Klaas van Breugel
Keyword(s):  
Alkaline Medium ◽  
Open Circuit Potential ◽  
Dynamic Equilibrium ◽  
Chloride Concentration ◽  
Chloride Content ◽  
Cementitious Materials ◽  
Open Circuit ◽  
Potentiometric Response ◽  
Before And After ◽  
The Stability

The stability and reproducibility of an Ag/AgCl sensors’ response in an alkaline medium are important for the application of these sensors in cementitious materials. The sensors’ response, or their open circuit potential (OCP), reflects a dynamic equilibrium at the sensor/environment interface. The OCP response in an alkaline medium is affected by the presence of hydroxide ions. The interference of hydroxide ions leads to inaccuracies or a delay in the sensors’ response to a certain chloride content. In this article, the potentiometric response (or OCP evolution) of the chloride sensors is measured in model solutions, resembling the concrete pore water. The scatter of the sensors’ OCP is discussed with respect to the interference of hydroxide ions at varying chloride concentration in the medium. The deviation of the sensor’s response from its ideal performance (determined by the Nernst law) is attributed to dechlorination of the AgCl layer and the formation of Ag2O on the sensor’s surface. Results from the surface XPS analysis of the AgCl layer before and after treatment in alkaline medium confirm these observations in view of chemical transformation of AgCl to Ag2O.

Adsorption and Oxidation of Thiosulfate on the Platinum Electrode in a Slightly Alkaline Medium

2000 ◽  
Vol 65 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Tomáš Loučka
Keyword(s):  
Alkaline Medium ◽  
Oxidation Reaction ◽  
Open Circuit Potential ◽  
Platinum Electrode ◽  
Adsorbed Layer ◽  
Open Circuit ◽  
Adsorbed Hydrogen ◽  
Oxidation Number ◽  
Hydrogen Electrode ◽  
Layer Region

The aim of this research was to study the oxidation and reduction of the adsorbed thiosulfate on the platinum electrode in a slightly alkaline medium. The adsorption was performed at the open circuit conditions. The reduction of the adsorbed layer in the hydrogen region is slower in a slightly alkaline medium than in acid. The mechanism of reduction and oxidation of adsorbed molecules is probably the same. The nonstationary currents measured in presence of thiosulfates showed that the change in the oxidation number does not take place during the adsorption in the double layer region. In the hydrogen region, thiosulfate replaces the adsorbed hydrogen while beeing reduced. Nonstationary currents at higher concentrations of thiosulfate indicate the presence of more layers on the electrode. Upon reaching higher concentrations of thiosulfate the oxidation reaction takes place between thiosulfate in solution and adsorbed product of its reduction. The open circuit potential of the platinum electrode measured in a thiosulfate solution was 0.780 and 0.783 V against the hydrogen electrode in the same solution.

Aluminium corrosion studies. IV. Pitting corrosion

1978 ◽  
Vol 31 (5) ◽  
pp. 943 ◽  
Author(s):  
RT Lowson
Keyword(s):  
Open Circuit Potential ◽  
Chloride Concentration ◽  
Open Circuit ◽  
Aluminium Chloride ◽  
Bulk Solution ◽  
Pitting Potential ◽  
Functional Relationships ◽  
Corrosion Studies ◽  
Thermodynamic Equilibrium Condition ◽  
Chloride Activity

Measurements are reported for the variation of the open-circuit potential, Er, of aluminium in oxygen-saturated sodium salt solutions. The value of Er was independent of SO42- and NO3- concentrations and similar to the value obtained for water (0.04 (s.h.e.)). Er was a function of chloride concentration given by ������������������� Er = -0.475-0.060log[Cl-] V (s.h.e.) at 25�C. There was a less well defined relationship between Er and NO2-, I- and Br-, and a complex relationship with F-. ��� The potentiodynamic characteristics are reported for aluminium in 1-0.01 mol l-1 Cl- oxygen-saturated solutions. Functional relationships were found for E0, Ep, Es and E0' with chloride activity at 5, 25, 50 and 75°C. Hysteresis effects are reported. ��� The experimental results are interpreted in terms of a thermodynamic equilibrium condition between the surface oxide and soluble aluminium chloride. As the system oscillates across the equilibrium conditions the surface will passivate or pit. A critical bulk solution chloride concentration is necessary to maintain the growth of the pit; the experimental value was 1.6 mol l-1 Cl- and the corresponding open-circuit potential was Ecrit = -0.48 V (s.h.e.). The pitting potential, Ev, was interpreted as an overpotential, ηp, given by η = Ep,- Ep-Ecrit.

Comparative Study of Structure and Pickling Characteristics of Oxide Scale Formed on Strips Produced by TSCR and Conventional Process

2011 ◽  
Vol 228-229 ◽  
pp. 77-82
Author(s):  
L. M. Zhu ◽  
J. H. Yang
Keyword(s):  
Oxide Scale ◽  
Open Circuit Potential ◽  
Steel Strip ◽  
Open Circuit ◽  
Conventional Process ◽  
Pickling Solution ◽  
Magnetite Fe3o4 ◽  
Structure Observation ◽  
The Stability ◽  
Hematite Fe2o3

The microstructure and pickling characteristics of oxide scale formed on hot-rolled SPHC steel strip produced by different processes were investigated based on structure observation, weight loss and corrosion potential measurements. The results show that the scale formed on strip produced by TSCR consists of mainly magnetite (Fe3O4) and little wustite (FeO), hematite (Fe2O3), and that in conventional process is composed mainly wustite (FeO) and little magnetite (Fe3O4), hematite (Fe2O3). The shape of the open-circuit potential transient is determined crucially by the oxide scale structure. Time to reach a steady-state value of open-circuit potential of strip produced by TSCR is longer than that in conventional process. Both the stability of the scale in pickling solution and the effectiveness of descaling could be evaluated and predicted by measuring the change of electrochemical potential during acid pickling.

Monitoring the Electrochemical Response of Chloride Sensors Embedded in Cement Paste

2015 ◽  
Vol 1768 ◽  
Author(s):  
F. Pargar ◽  
D.A. Koleva ◽  
E.A.B. Koenders ◽  
K. van Breugel
Keyword(s):  
Cement Paste ◽  
Electrochemical Impedance ◽  
Chloride Concentration ◽  
External Solution ◽  
Chloride Content ◽  
Open Circuit ◽  
Water Soluble ◽  
Free Chloride ◽  
Chloride Determination ◽  
Bound Chloride

ABSTRACTThis work presents the electrochemical behavior of Ag/AgCl electrodes (chloride sensors) in cement paste environment, monitored over a period of 180 days via open circuit potential (OCP) readings and electrochemical impedance spectroscopy (EIS). The EIS response indicates modification of the sensors’ morphology, in particular alteration of the AgCl layers, as a result of continuous chloride penetration into the bulk matrix towards the vicinity of the sensor/cement paste interface. A gradual shift to more cathodic OCP values and stabilization at approximately -1mVSCE to 2mVSCE was observed at the end of the test, reflecting chloride content of 820mM to 930mM in the pore solution surrounding the sensors, which differs 5-10% from the chloride concentration in the external solution. The water soluble chloride content in the cement pate, as destructively measured wet chemically by Volhard method and photometry, was in the range of 1100mM - 1300mM i.e. about 30-50% more than the chloride concentration in the external solution. This difference of maximum 50% in the recorded chloride levels is attributed to the fact that the sensors “read” the average amount of free chloride at the interface sensor/cement paste, while the destructively measured water soluble chloride reflects the average free (with possible contribution of physically bound chloride) in the total volume of analyzed cement paste. It can be concluded that for the conditions of this experiment, more reliable free chloride content is measured via the sensors’ readings. Hence, if chloride thresholds for corrosion initiation are to be determined, the sensors’ readings will be more representative and accurate if compared to destructive water soluble chloride determination.

Corrosion of Carbon Steel in Nanofluid Containing ZrO2 Nanoparticle at Different Temperature

2014 ◽  
Vol 896 ◽  
pp. 168-172 ◽  
Author(s):  
Djoko Hadi Prajitno ◽  
Dani Gustaman Syarief
Keyword(s):  
Carbon Steel ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Positive Displacement ◽  
Steel Increase ◽  
Polarization Technique ◽  
Before And After ◽  
Increasing Temperature

Corrosion of carbon steel in nanofluid containing 0.1 gpl of ZrO2nanoparticle at temperature from 25 to 55°C was investigated by using potentiodynamic polarization techniques. The open circuit potential measurements, cathodic and anodic polarization were used to characterize the corrosion behavior of carbon steel. Metallurgical techniques such as optical microscopy and X-ray diffraction (XRD) were used to characterize the alloys before and after corrosion testing. The microstructures of the as received carbon steel exhibited equaxed morphology. While corrosion specimens showed that microstructure of carbon steel alloys relatively unchanged after polarization testing. X ray diffraction examination of carbon steel before polarization represent γ phase and after polarization is still γ phase with minor Fe2O3. The open circuit potentials of carbon steel increase to positive displacement with increasing temperature nanofluids. The results of polarization technique show that corrosion currents increase and therefore corrosion rates become faster with the increase of nanofluids temperature.

scholarly journals Origins of the Instability of Non-precious HER Catalysts at Open Circuit Potential

2021 ◽  
Author(s):  
Zhenbin Wang ◽  
Ya-Rong Zheng ◽  
Joseph H. Montoya ◽  
Degenhart Hochfilzer ◽  
Ang Cao ◽  
...  
Keyword(s):  
Working Conditions ◽  
Inductively Coupled Plasma ◽  
Open Circuit Potential ◽  
Acidic Solution ◽  
Open Circuit ◽  
Inductively Coupled ◽  
Pourbaix Diagrams ◽  
Interface Potential ◽  
Thermodynamic Driving Force ◽  
The Stability

<p>Non-precious hydrogen evolution reaction (HER) catalysts commonly suffer from severe dissolution under open circuit potential (OCP). In this work, using calculated Pourbaix diagrams, we quantitatively analyze the stability of a set of well-known active HER catalysts (MoS<sub>2</sub>, MoP, CoP, Pt in acid, and Ni<sub>3</sub>Mo in base) under working conditions. We determine that the large thermodynamic driving force towards decomposition created by the electrode/electrolyte interface potential is responsible for the substantial dissolution of non-precious HER catalysts at OCP. Our analysis further shows the stability of HER catalysts in acidic solution is ordered as Pt ∼ MoS<sub>2 </sub><i>> </i>MoP <i>> </i>CoP, which is confirmed by the measured dissolution rates using an inductively coupled plasma mass spectrometer. Based on gained insights, we suggest strategies to circumvent the catalyst dissolution in aqueous solution.</p>

scholarly journals Adsorption characteristics of albumin on gold and titanium metals in Hanks’ solution using EQCM

2004 ◽  
Vol 18 (4) ◽  
pp. 545-552 ◽  
Author(s):  
J. A. Lori ◽  
T. Hanawa
Keyword(s):  
Bovine Serum Albumin ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Open Circuit Potential ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Open Circuit ◽  
Rest Potential ◽  
Before And After ◽  
Titanium Surfaces ◽  
Adsorption Desorption

The adsorption of Bovine Serum Albumin (BSA) on gold and titanium surfaces in Hanks’ solution was monitored using the electrochemical quartz crystal microbalance (EQCM) technique. The changes in mass and open circuit potential at rest potential and mass and current at constant potentials were measured before and after the introduction of BSA.The mass of BSA adsorbed on titanium reached a steady value within one hour, while the albumin adsorbed on gold continued to increase. The amount of BSA adsorbed by titanium increased with concentration and stabilized at 0.8 mg/ml while that on gold did not stabilize. This indicates a monolayer of the protein on titanium and multi-layer on gold. The adsorption of BSA on gold and titanium was accelerated by the charge of potential.The time before stabilizing the adsorption‒desorption phenomena also increased with the BSA concentration.

scholarly journals Corrosion and Electrochemical Properties of Nanocrystalline W-Mo Alloys in NaOH Solutions

1970 ◽  
Vol 11 ◽  
pp. 147-152
Author(s):  
Arun Khadka ◽  
Jagadeesh Bhattarai
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Properties ◽  
Open Circuit Potential ◽  
Science And Technology ◽  
Open Circuit ◽  
Sputter Deposition ◽  
Corrosion Tests ◽  
Corrosion Rates ◽  
Sputter Deposited ◽  
The Stability

The corrosion and electrochemical properties of sputter-deposited nanocrystalline binary W-Mo alloys were studied after immersion for 2429 h in different concentrations of NaOH solutions open to air at 25°C using corrosion tests and open circuit potential measurements. Molybdenum acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited binary W-Mo alloys so as to show higher corrosion resistance than those of alloy-constituting elements (i.e. tungsten and molybdenum) after immersion for 24 h in NaOH solutions. Open circuit potentials of all the examined sputter-deposited W-Mo alloys are shifted to the more positive (noble) direction with increasing molybdenum content in the alloys. The stability of the spontaneously passivated films formed on the binary W-Mo alloys is decreased with increasing concentrations of NaOH solutions. In spite of these facts, the corrosion rates of all the examined W-Mo alloys are almost independent of concentrations of NaOH solutions after immersion for 24 h at 25°C.Key words: nanocrystalline W-Mo alloys; sputter deposition; corrosion resistance; open circuit potential; NaOH solutions DOI: 10.3126/njst.v11i0.4137Nepal Journal of Science and Technology 11 (2010) 147-152

A PROPOSAL FOR MODIFIED GALVANIC CORROSION MODEL: INVESTIGATING EFFECTS OF MICRO-ARC OXIDATION ON Al ALLOY

2019 ◽  
Vol 26 (02) ◽  
pp. 1850147
Author(s):  
YUANHANG YANG ◽  
YANHONG GU ◽  
JIAN LIANG ◽  
WEN YUE
Keyword(s):  
Open Circuit Potential ◽  
Galvanic Corrosion ◽  
Open Circuit ◽  
Al Alloy ◽  
Corrosion Mechanism ◽  
Corrosion Performance ◽  
Before And After ◽  
Micro Arc Oxidation ◽  
Corrosion Behaviors ◽  
Micro Structures

Corrosion is generally an undesirable phenomenon in most engineering applications. The effects of micro-arc oxidation (MAO) coating on Al alloy on the galvanic corrosion performance have been studied. The surface micro-structures were characterized using scanning electron microscope (SEM) and metallographic microscope before and after corrosion. Electrochemical studies on the corrosion behaviors have been reported by using open circuit potential (OCP) and potentiodynamic polarization (PDP) measurements in a slurry solution. All measurements were consistent with each other and showed that the MAO coating can significantly reduce the corrosion rate of Al alloy. A model for elucidating corrosion mechanism and corrosion process of the MAO coating on Al alloy is proposed.

Corrosion Performance of Mild Steel in Paper Mill Effluent

2012 ◽  
Vol 585 ◽  
pp. 522-527 ◽  
Author(s):  
Chhotu Ram ◽  
Chaya Sharma ◽  
Ajay Kumar Singh
Keyword(s):  
Mild Steel ◽  
Open Circuit Potential ◽  
Corrosion Behaviour ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Chloride Content ◽  
Paper Mill ◽  
Open Circuit ◽  
Localized Corrosion ◽  
Paper Mill Effluent

Present paper reports investigations carried on corrosion behaviour of mild steel in effluents collected from paper mill treatment plant. For this purpose, effluent was collected from after primary and secondary treatment stages. Mild steel samples were exposed to these effluents for duration of six months. The corroded samples were analysed for weight loss and extent of localised corrosion. Electrochemical polarization tests like open circuit potential (OCP), tafel plot and anodic polarization were also performed to estimate corrosion rate, polarization resistance and localized corrosion parameters in the studied system. The extent of corrosion attack has been correlated with effluent parameters namely pH, electrical conductivity (Ec), total suspended solids, total dissolved solids, chemical oxygen demand, biochemical oxygen demand, chloride content, colour and sulphate.

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