20.500.12556/DKUM-26719 Tungsten - tungsten trioxide electrodes for the long-term monitoring of corrosion processes in highly alkaline media and concrete-based materials The determination of pH in highly alkaline solutions and concrete materials is extremely important for monitoring or predicting the corrosion processes of reinforced concrete structures and to follow the hydration process of Portland cement, fly-ash, micro silica and other materials used in concrete manufacturing. The corrosion of reinforced concrete structures and the hydration of pozzolanic materials are long-term processes, which means, that appropriate durable, and resilient pH electrodes are needed, for direct implantation regarding solid concrete bodies. The purpose of this work was to characterise the potentiometric and surface properties of tungsten electrodes after exposure to extreme alkaline solutions. The tungsten wire surface was activated at 800 °C for 30 min within an oxygen flow. The formation of homogenous and compact multiple layers of $WO_3$ crystals was observed using X-ray diffraction and scanning electron microscopy. X-ray diffraction of thosetungsten electrodes exposed to saturated calcium hydroxide solution or the pore-water of cement-based materials during 10 months, indicated partly dissolved $WO_3$. Two new compounds appeared on the electrodes surfaces; pure tungsten and $CaWO_4$. The presence of tungsten was affecting any potentiometric response in acidic pH region (2-5) but in pH 5-12 region the response still remained linear with a slope of 42 2 mV/pH unit. The $W/WO_3$ electrode was suitable for the long-term monitoring of corrosion processes in concrete-basedmaterials according to the pH changes as it has stable and repeatable responses to alkaline solutions (pH > 12). All the tested interferring ions had no significant influence on electrode potential. The $W/WO_3$ electrode is simple, robust, inexpensive, and temperature resistant and can be applied in potentiometric titrations as well as in batch and flow-injection analysis. The prepared electrode is a highly promising pH sensor for the monitoring of pH changes in highly alkaline capillary water of concrete. Merjenje pH v močno alkalnih raztopinah in v betonskih vzorcih je zelo pomembno za napoved korozije armature, kakor tudi za spremljanje drugih hidratacijskih procesov materialov, ki se uporabljajo pri proizvodnji betona. Tovrstni procesi so dologotrajni in zahtevajo robustne, vzdržljive in enostavne pH senzorje, ki omogočajo tudi neposredno namestitev v betonsko matriko. V delu so predstavljene $W/WO_3$ elektrode, ki so bile aktivirane pri 800 °C za 30 minut, pri čemer je na površini nastala homogena in stabilna plast $WO_3$. Tudi dolgotrajna, 10 mesečna izpostavitev v nasičeni raztopini $Ca(OH)_2$, kaže na nespremenjene potenciometrične lastnosti elektrod v območju med pH 5 in 12 z naklonom 42 ± 2 mV/pH. Preizkušeni interferenčni ioni niso imeli signifikantnega vpliva na elektrodni potencial. $W/WO_3$ elektrode so se izkazale kot enostaven, dostopen, temperaturno obstojen in obetaven pH senzor, ki ga lahko uporabljamo tako za klasične potenciometrične titracije kot meritve v pretoku. Še posebej $W/WO_3$ elektrode odlikuje dobro ponovljiv odziv v močno alkalnih raztopinah (pH > 12), kar nakazuje uporabo pri določanju pH vrednosti kapilarne vode ter in-situ meritvah v betonu. potentiometry pH tungsten - tungsten trioxide pore water concrete flow-injection analysis potenciometrija pH volframov trioksid true false true Angleški jezik Slovenski jezik Znanstveno delo 2012-05-31 14:48:28 2012-05-31 14:48:28 2022-04-15 13:32:26 2024-01-03 03:34:50 2010 0 0 str. 813-820 št. 4 Letn. 57 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1318-0207 543.5:691 14086149 14701078 1318-0207 URN:SI:UM:DK:PUZTRJQG Acta_Chimica_Slovenica_2010_Kolar_et_al._Tungsten_-_tungsten_trioxide_electrodes_for_the_long-term_monitoring_of_corrosion_processes_in.pdf Acta_Chimica_Slovenica_2010_Kolar_et_al._Tungsten_-_tungsten_trioxide_electrodes_for_the_long-term_monitoring_of_corrosion_processes_in.pdf 1 67A8D5FA5990FC0E07E33B50054174A9 cec49a9276bda3d883c7a8ebaeffd34805f4cc931f3dfea36e567f84e3497e32 3328ed31-7c07-11eb-bb7a-00155d0001ca 20.500.12556/dkum/fa792d19-93e7-4421-ae35-162e4525f534 https://dk.um.si/Dokument.php?lang=slv&id=116387 http://acta-arhiv.chem-soc.si/57/57-4-813.pdf 1 https://dk.um.si/Dokument.php?lang=slv&id=116388 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0