A Mechanical–Electrochemical Approach for the Determination of Precursor Sites for Pitting Corrosion at the Microscale

Palm oil is one of the major oils and fats produced in the world today. The quality of palm oil is crucial to be investigated, and one of the quality indices is free fatty acid (FFA) content. Therefore, in this study, an electrochemical approach for the determination of FFA has been explored as an alternative to replace the conventional method (titration method). The electrochemical method was developed based on electrochemically reduced graphene oxide (rGO) coupled with gold nanoparticles (AuNPs) deposited onto a screen-printed carbon electrode (SPCE) via drop-casting technique. The voltammetric behaviour of 2-methyl-1,4-naphthoquinone (VK3) in the presence of palmitic acid at the modified electrode was investigated in an acetonitrile/water mixture containing lithium perchlorate (LiClO4). The electrochemical detection of palmitic acid was based on the voltammetric reduction of VK3 to form the corresponding hydroquinone which is proportional to the concentration of palmitic acid. Under optimum conditions, the developed method showed a good linear relationship towards palmitic acid in the concentration ranging from 0.192 mM to 0.833 mM with the detection limit of 0.015 mM. The exploration of the developed system is expected to achieve high sensitivity and excellent selectivity towards the determination of FFA content in palm oil.

Download Full-text

Determination of the size of cavities in pitting corrosion by radiographic contrast measurement / Détermination radiographique de la corrosion par piqȗre à l'aide de la mesure de contraste / Radiographische Bestimmung der Lochfraßtiefe mittels Kontrastmessung

Materials Testing ◽

10.1515/mt-1964-061002 ◽

1964 ◽

Vol 6 (10) ◽

pp. 343-346

Author(s):

A. de Sterke

Keyword(s):

Pitting Corrosion ◽

Radiographic Contrast ◽

Contrast Measurement

Download Full-text

Determination of the Life Cycle of Heat-Exchange Tubes of Vapor Condensers on the Basis of Statistical Analysis of Local Pitting Corrosion According to Data of Eddy Current Testing

Protection of Metals and Physical Chemistry of Surfaces ◽

10.1134/s2070205118060138 ◽

2018 ◽

Vol 54 (6) ◽

pp. 1221-1232 ◽

Cited By ~ 2

Author(s):

V. A. Golovin ◽

N. V. Pechnikov ◽

V. A. Shchelkov ◽

A. Yu. Tsivadze

Keyword(s):

Life Cycle ◽

Statistical Analysis ◽

Heat Exchange ◽

Eddy Current ◽

Pitting Corrosion ◽

Eddy Current Testing ◽

Current Testing

Download Full-text

Low Potential Pitting Corrosion of Ni-Cr-Fe Alloys in Chloride Plus Thiosulfate Solutions: Determination of Potential and Concentration Boundaries

CORROSION ◽

10.5006/3562 ◽

2020 ◽

Vol 76 (8) ◽

pp. 786-795

Author(s):

Abraham A. Becerra Araneda ◽

Mariano A. Kappes ◽

Martín A. Rodríguez ◽

Ricardo M. Carranza

Keyword(s):

Pitting Corrosion ◽

Chloride Ions ◽

Aged Alloy ◽

Electrochemical Tests ◽

Alloy 800 ◽

Chloride Threshold ◽

Alloy 690 ◽

Fe Alloys ◽

Thiosulfate Concentration

Low potential pitting corrosion (LPPC) of Alloys 690 and 800 (UNS N06690 and N08800) was studied in neutral solutions, containing chloride ions from 0.1 M to 1 M and thiosulfate ions from 5 × 10−5 M to 10−3 M. LPPC occurred close to the corrosion potential (–0.25 VAg/AgCl) by a synergic effect of the chloride and thiosulfate ions. The threshold concentrations of aggressive species for LPPC occurrence were identified by potentiostatic tests with mechanical scratching of the surface, which yielded more conservative estimations compared to other electrochemical tests. The ranges of potential and concentration of chloride and thiosulfate where LPPC occurred and where it merged with the conventional chloride pitting were determined. The lowest threshold concentrations were measured in Alloy 800, with a lower Cr content than Alloy 690. Thermally-aged Alloys 800 and 690 had lower resistance to LPPC than the corresponding solution-annealed material. In 1 M chloride-based solutions, for aged Alloy 800, LPPC occurred at a thiosulfate concentration as low as 5 × 10−5 M; in 10−3 M thiosulfate-based solutions, the chloride threshold was 0.1 M. For thermally-aged alloys, pits propagated intergranulary in some experiments. In solutions with chloride and thiosulfate concentrations close to the threshold required for pitting, repassivation of LPPC was observed after a sustained period of pit growth, originally initiated by scratching the surface. Such a repassivation has not been reported before in the literature in chloride and thiosulfate solutions. Two possible explanations were presented for this phenomenon.

Download Full-text

The Relationship Between Repassivation Behavior and Pitting Corrosion for Ti and Ti6AI4V

CORROSION ◽

10.5006/0010-9312-34.12.437 ◽

1978 ◽

Vol 34 (12) ◽

pp. 437-442 ◽

Cited By ~ 22

Author(s):

H. -J. RAETZER-SCHEIBE

Keyword(s):

Corrosion Behavior ◽

Pitting Corrosion ◽

Metallic Surface ◽

Current Time ◽

The Relationship ◽

Current Potential ◽

Potential Curves

Abstract The characteristic pitting potentials of Ti and Ti6AI4V were determined by measurement of potentiodynamic current-potential curves in solutions of 1N NaCl, 1N Nal, and 1N NaBr. Under the same conditions current-time curves were measured for various potentials after generation of a new metallic surface. By means of these curves, one can study the repassivation behavior of materials. The comparison between the potential of pit repassivation and the repassivation/nonrepassivation potential shows a relatively good correlation. The determination of the critical repassivation potentials enables us to predict the pitting corrosion behavior.

Download Full-text

Lab-on-a-Chip Device for Hydrogen Sulfide Sensing in Biomedical and Environmental Applications Using Electrochemical Approach

Volume 3: Advanced Fabrication and Manufacturing; Emerging Technology Frontiers; Energy, Health and Water- Applications of Nano-, Micro- and Mini-Scale Devices; MEMS and NEMS; Technology Update Talks; Thermal Management Using Micro Channels, Jets, Sprays ◽

10.1115/ipack2015-48491 ◽

2015 ◽

Cited By ~ 2

Author(s):

A. Baniya ◽

S. Thapa ◽

E. Borquist ◽

D. Bailey ◽

D. Wood ◽

...

Keyword(s):

Hydrogen Sulfide ◽

Direct Detection ◽

Sulfide Oxidation ◽

Lab On A Chip ◽

Electrode System ◽

Sulfide Concentration ◽

Pt Electrodes ◽

Electrochemical Approach ◽

And Performance

Hydrogen sulfide (H2S) is rapidly emerging as a biologically significant signaling molecule. In recent studies, sulfide level in blood or plasma has been reported to be in the concentration between 10 and 300 μM suggesting it acts in various diseases. This work reports progress on a new Lab-on-a-Chip (LOC) device for these applications. The uniquely designed, hand-held device uses advanced liberation chemistry that releases H2S from liquid sample and an electrochemical approach to detect sulfide concentration from the aqueous solution. The device itself consists of three distinct layers of Polydimethylsiloxane (PDMS) structures and a three electrode system for direct and rapid H2S concentration measurement. In this work specifically, the oxidation of sulfide at the gold (Au) and platinum (Pt.) electrodes has been examined. This is the first known application of electrochemical H2S sensing in an LOC application. The analytical utility and performance of the device has been assessed through direct detection using chronoamperometry (CA) scan and cyclic voltammetry (CV). An electrocatalytic sulfide oxidation signal has been recorded for sulfide concentration range vs, Ag/AgCl at different pH buffers at the trapping chamber. The calibration curve in the range 1 μM to 1 M was obtained using this electrode setup. The detection limit was found to be 0.1 μM. This device shows promise for providing fast and inexpensive determination of H2S concentration in aqueous samples.

Download Full-text