Ingenieurwissenschaften und zugeordnete Tätigkeiten
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Electrochemical study of polyaniline/silicon dioxide containing coatings in geothermal solution
(2018)
Polyaniline/Silicon Dioxide containing coatings were electrochemically investigated in a saline geothermal solution.
With the increase of exposure time, impedance values of coated specimens decreased at low frequency, which could be caused by the decrease of pore resistance due to electrolyte or water uptake.
Coating system needs further optimization work.
Geothermal brine is a complex system containing a wide variety of dissolved salts resulting from the condition s in a geothermal well. These fluids lead to corrosion in pipes and other parts of geothermal system construction and necessitate intense research efforts in finding new suitable materials. Carbon steel is susceptible to corrosion in geothermal brine especially when it is exposed to a high temperature and high-pressure medium, which is considered to be an aggressive environment. An artificial geothermal water, bas ed on a brine composition found in Indonesia, was used to investigate the performance of high alloyed materials. The electrolyte has pH 4 and contains 1,500 mg/l Cl-, 20 mg/l SO4 2-, 15 mg/l HCO3 -, 200 mg/l Ca 2+, 250 mg/l K+, and 600 mg/l Na+. In order to protect the bare material in geothermal application, it is necessary to either use high alloyed material s or coatings. In this research, a coating system consisting of polyaniline and silicon dioxide was investigated regarding its behavior to protect carbon steel. In detail, the effect of SiO2 and polyaniline (PANi) addition was evaluated by exposure and electrochemical tests for 7 days, i.e. electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) at room temperature and 150 °C with 1 MPa pressure.
Electrochemical deposition of polyaniline on carbon steel for corrosion study in geothermal solution
(2018)
Polyaniline has been widely developed for many applications, e.g., sensor, supercapacitor component, electrochromic devices, and anticorrosion pigments [1]. Although the addition of polyaniline pigment in organic coatings has been an alternative for corrosion protection in industrial application, the protection mechanism is still not fully understood [2]. Herein in this study, as a part of the development of polyaniline/silicon dioxide coating for geothermal application, polyaniline has been deposited electrochemically on carbon steel surface and tested in geothermal solution to study the contribution of polyaniline in the corrosion protection of a polyaniline-based composite in the geothermal system. The electrochemical deposition was carried out by immersing carbon steel in 0.1 M oxalic acid and 0.05 M aniline, with the polarization potential of -0.6 – 1.5 V vs. Ag/AgCl, and a scan rate of 10 mV/s. To observe the surface/interface reaction between the electrolyte and electrode surface during the electrochemical polymerization, electrochemical impedance spectroscopy (EIS) measurement was applied after each cycle. For corrosion study in the geothermal application, this experiment used an artificial geothermal solution with the composition of 1,500 mg/l Cl-, 20 mg/l SO42-, 15 mg/l HCO3-, 200 mg/l Ca2+, 250 mg/l K+, and 600 mg/l Na+, and pH 4 to simulate a geothermal brine found in Sibayak, Indonesia. Electrochemical measurements were performed by monitoring the open circuit potential over seven days, with the interruption of EIS every 22 hours. The experiments were performed at room temperature and 150 °C (1 MPa) in a free oxygen environment. Polyaniline coated carbon steel is more durable in a room temperature environment compared to 150 °C, which could be caused by the iron oxalate dissolution at elevated temperature. This degradation was further proven by the impedance spectra, which showed a reduction of approximately ten times for specimens measured at 150 °C as compared to the specimens measured at room temperature.
Geothermal brine is a complex system containing a wide variety of dissolved salts resulting from the condition s in a geothermal well. These fluids lead to corrosion in pipes and other parts of geothermal system construction and necessitate intense research efforts in finding new suitable materials. Carbon steel is susceptible to corrosion in geothermal brine especially when it is exposed to a high temperature and high-pressure medium, which is considered to be an aggressive environment. An artificial geothermal water, bas ed on a brine composition found in Indonesia, was used to investigate the performance of high alloyed materials. The electrolyte has pH 4 and contains 1,500 mg/l Cl-, 20 mg/l SO4 2-, 15 mg/l HCO3 -, 200 mg/l Ca 2+, 250 mg/l K+, and 600 mg/l Na+. In order to protect the bare material in geothermal application, it is necessary to either use high alloyed material s or coatings. In this research, a coating system consisting of polyaniline and silicon dioxide was investigated regarding its behavior to protect carbon steel. In detail, the effect of SiO2 and polyaniline (PANi) addition was evaluated by exposure and electrochemical tests for 7 days, i.e. electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP ) at room temperature and 150 °C with 1 MPa pressure .
Der Vortrag stellt ein neuartiges Korrosionsprüfverfahren für Zinküberzüge auf Basis gelartiger Elektrolyte vor und führt die Vorteile gegenüber konventionellen Prüfverfahren auf. Basierend auf den Ergebnissen wird die Idee für einen IGF-Projektantrag in Kooperation mit dem Fraunhofer IKTS vorgestellt.
A new approach to the assessment of the corrosion behaviour of zinc coatings under atmospheric conditions can be achieved using gel-type electrolytes as an alternative to standard aqueous test electrolytes. Gel-type electrolytes allow minimally invasive corrosion investigations on zinc coatings. They also provide the possibility to carry out corrosion investigations onsite. By using gel-type electrolytes corrosion-relevant characteristic values such as corrosion currents and polarization resistanc-es can be determined. These allow to describe the formation and the stability of the formed corrosion product layers under various climatic conditions. With this knowledge, a prediction of the zinc coating life cycle is possible. In this contribution, the value of gel-type electrolytes for corrosion research on zinc coatings is presented.
A new approach to the assessment of the corrosion behaviour of zinc coatings under atmospheric conditions can be achieved using gel-type electrolytes as an alternative to standard aqueous test electrolytes. Gel-type electrolytes allow minimally invasive corrosion investigations on zinc coatings. They also provide the possibility to carry out corrosion investigations onsite. By using gel-type electrolytes corrosion-relevant characteristic values such as corrosion currents and polarization resistances can be determined. These allow to describe the formation and the stability of the formed corrosion product layers under various climatic conditions. With this knowledge, a prediction of the zinc coating life cycle is possible. In this contribution, the value of gel-type electrolytes for corrosion research on zinc coatings is presented.