The authors had no funding provided for this study.

1. Construção do Titular da Amostra <ol><li> Construir porta-amostras e espaçadores de aço inoxidável e um parafuso de aço inoxidável M3 rosca, mantido no lugar com uma porca hexagonal M3. </li><li> Retire a cabeça do parafuso de rosca usando um alicate e polir o segmento de corte para manter o padrão de discussão. </li><li> Quando todos os componentes individuais estão prontos, montar os suportes de eléctrodos. Cada titular eletrodo contém três espaçadores unidas por parafusos M3, resultando em uma alça de 11,5 cm. Coloque as porcas hexagonais na junção do parafuso e espaçadores para bloquear a ligação. </li><li> Solda (60/40% Sn / Pb) uma pinça sem dentes para a rosca na extremidade da haste. Isso irá garantir uma firma espera para anexar mais tarde, o eletrodo durante a análise. </li><li> Uma vez que os titulares de eléctrodos são montados, aplicar várias camadas de verniz stop-off (selante elétrico) para impedir que as hastes de aço inoxidável da corrosão, enquanto imersa na câmara de corrosão. <ol><li> Coloque todos os titulares de eléctrodos com as amostras associadas ao jacaré em um exaustor antes do revestimento. Coloque uma seringa de 20 ml para a capela. Use a seringa para recolher o verniz stop-off. </li><li> Ligue o exaustor e despeje a laca stop-off em um pequeno frasco de vidro. Retire 10 ml de paragem laca para dentro da seringa e revestir a superfície dos suportes de eléctrodos. Certifique-se de não cobrir a amostra de teste, que vai ser analisado para corrosão. </li><li> Brasão metade de cada suporte do eletrodo e coloque na coifa para secar antes de aplicar a outra metade. Isto irá ajudar a obter uma camada bem fechado completo, sem danificar as zonas a serem revestidas. Certifique-se de que, durante a fase de secagem, as regiões recém-revestidos não toque outras superfícies, como isso irá arruinar o revestimento aplicado. </li><li> Coloque os porta-eletrodos em uma posição elevada durante a secagem, sem contato com qualquer superfície. Revestir os eletrodos rapidamente, devido ao rápido solidificação da laca stop-off.Isto conclui a primeira camada. </li><li> Depois de seco, repetir o processo para se obter 3 camadas ao longo de toda a área. </li></ol></li><li> Antes de iniciar a corrosão prazo, deixar os titulares para secar por 24 horas após a conclusão do revestimento final. Todos os processos de revestimento ocorrer a RT, sem aquecimento ou arrefecimento passos são necessários, embora possam acelerar / desacelerar o processo de cura. </li><li> Fazendo uma gaiola de Faraday <ol><li> Construir uma gaiola de Faraday por revestimento de dois recipientes de plástico do mesmo tamanho com 4 camadas de folha de alumínio para cobrir todos os lados. </li><li> Corte dois pequenos furos para fora na borda superior do recipiente de plástico para permitir a ligação do eléctrodo para o potenciostato e a linha de azoto para o tanque de azoto ao passar. Um design da separação da gaiola de Faraday permite que o componente superior para ser removido no final de uma execução, sem a necessidade de substituir a secção inferior que aloja o tanque. </li><li> Montar o compartimento externo (câmara de água) para a gaiola de Faraday. leavÊ O segundo meio para o lado e coloque em cima do compartimento inferior apenas quando o recipiente foi selado corrosão (no final do procedimento). </li></ol></li></ol> 2. Limpeza de artigos de vidro <ol><li> Limpe o recipiente de corrosão (700 ml balão cilíndrico) antes de cada corrosão prazo. Esfregue o recipiente com detergente e enxaguar abundantemente com água da torneira. Repita este passo 3 vezes. </li><li> Lavar o recipiente de corrosão 3 vezes com água deionizada água (DI) para remover potenciais contaminantes encontrados na água da torneira. </li><li> Uma vez que a lavagem com água desionizada é completada despeje 300 ml de etanol a 95% para o vaso de corrosão e rodam ao redor para entrar em contato com todas as superfícies internas. Derramar o etanol e repita este passo 3 vezes. </li><li> Deixar o recipiente de corrosão sob um exaustor de fumos, durante 30 min para permitir que todo o etanol se evaporar completamente. </li><li> Pegue a, embarcação corrosão limpo e seco e lave-o com o eletrólito que será usado para a corrosão prazo. para eACH enxaguar encher o recipiente com 200 ml de corrosão do electrólito e repetir este procedimento 3 vezes. Para este estudo, lavar o recipiente de corrosão com solução salina tamponada com fosfato (PBS). A composição química da (10 L) ao longo de electrólito utilizado PBS é de 80 g de NaCl, 11,5 g de Na 2 HPO 4, 2 g de KCl e 2 g KHPO 4. </li><li> Após a lavagem, encher o recipiente de corrosão com o volume necessário de PBS pronto para a reacção. </li></ol> 3. Configuração de Dispositivo <ol><li> Grampo um aquecedor com um sistema de circulação inerente para o lado do compartimento externo com uma braçadeira. O tamanho do compartimento externo deve ser cerca de 30 cm x 20 cm x 20 cm e são feitos de vidro ou de polímero a ser capaz de alojar o recipiente corrosão menor e o sistema do aquecedor. </li><li> Encher o compartimento exterior com água da torneira até que o nível de água é maior do que a altura dos eléctrodos em suspensão dentro do vaso de corrosão. O compartimento mais pequenoé o vaso de corrosão (descrito anteriormente na secção 2). </li><li> Selar o recipiente de corrosão com uma tampa de reacção de vidro e braçadeira para assegurar uma vedação impermeável. A tampa da câmara oferece seis pontos de entrada para aparato experimental e medição. </li><li> Suspender um termómetro de um dos pontos de entrada da tampa de reacção para proporcionar uma leitura da temperatura no interior da célula de corrosão. Suspender todas as três eletrodos da tampa usando os outros 3 pontos de entrada. Use fita de politetrafluoretileno (PTFE) para assegurar a vedação de cada ligação. </li><li> Usar uma configuração de três eléctrodos constituído por uma referência, contador e eléctrodo de trabalho. O eletrodo de trabalho é o parafuso de aço inoxidável (modelo em análise). Antes de inserir o eletrodo dentro do vaso corrosão, limpe com um etanol 80% encharcada limpe e coloque em um copo de vidro cheio com 100 ml de PBS. </li><li> Use um pino de conexão para anexar os titulares eletrodo para os suspensórios eletrodos. Montar o electrode suspensórios para os pontos de entrada da tampa do recipiente de corrosão. </li><li> Colocar o eléctrodo de trabalho centralmente com o eléctrodo contador e de referência a ser suspenso a partir de ambos os lados. Selar o ponto de entrada de vidro e os suspensórios corrosão usando fita PTFE. </li><li> Para o eléctrodo de referência, usar um padrão de Ag / AgCl. Para o contra-eletrodo, use uma malha de platina, que foi vagamente dobrado para envolver o espécime sob teste (trabalhando eletrodo). </li><li> Encher o eléctrodo de Ag / AgCl com 3 M KCl usando uma pipeta. Seguindo o uso extensivo, mudança e encher o Ag Ag / Cl. Para fazer este lançamento a ponta do eléctrodo para esvaziar o líquido em um recipiente de recolha de vidro pequeno (copo). Uma vez que toda a solução é removida inserir a ponta e encher com 3 M de KCl. </li><li> Use fita adesiva em todas as junções para garantir toda a câmara está selado. </li><li> Uma vez que a câmara é selada com todos os eléctrodos colocados dentro do recipiente de corrosão, ajustar a temperatura para 37 ° C e abrir a válvula de azoto witha vazão de 150 cm3 / min. Deixe a temperatura e nitrogênio em execução durante 60 min antes de realizar uma corrida. Continue correndo nitrogênio para a duração do experimento. </li></ol> 4. Executando Teste de Corrosão <ol><li> Abra o pacote de software eletroquímico, que faz interface com o potenciostato controlado USB. </li><li> Faça as conexões elétricas entre o potenciostato e os 3 eléctrodos e depois ligue o potenciostato diante. </li><li> Abrir e usar a &quot;visão de medição&quot; para visualizar as leituras atuais e potenciais do ambiente de corrosão. Durante a fase de potencial de circuito aberto (OCP), onde há potencial de rampa é ainda aplicada a leitura atual entre o trabalho (potencial positivo) e contra (negativo) eletrodo é de cerca de (0 ± 0,01) mA. A vedação inadequada da câmara com fita PTFE podem causar flutuações na leitura atual, devido à câmara a ser arejada com azoto para remover moléculas de oxigênio. </li><li> Deixe oprovar para equilibrar e estabilizar dentro do ambiente de navio corrosão. A duração do tempo para este varia (1-6 h) e é dependente do material. Monitorar o potencial de utilizar a vista de medição para determinar se as condições estabilizadas são atingidos. O potencial será constante sem oscilações quando as condições estáveis ​​são alcançados. </li><li> Depois de condições estáveis ​​são alcançados, iniciar a corrosão prazo. Contudo, antes de isso pode ser feito, preencher o &quot;programa de corrosão&quot; e &quot;voltametria cíclica (CV)&quot; condições usando o modelo de esqueleto fornecido pelo software analítico. </li><li> Selecione o procedimento voltammetry potenciostato cíclica dentro da visão de configuração a partir da guia procedimento. </li><li> Ative as seguintes parâmetros a serem amostrados para a corrosão de execução: o tempo, trabalhando eletrodo potencial (WE) e atual para a corrosão prazo. </li><li> Selecione a opção de automatizar a actual gama. Defina a maior corrente na faixa a ser 10 mA, e o menor atual no range ser 10 nA para o WE. </li><li> Garantir a selecção final cut-off é controlada através do potencial definindo o parâmetro &quot;ciclo back &#39;a 0,8 mV para permitir que o ciclo de histerese para ser concluído. </li><li> Grave a OCP a partir da vista de medição na caixa de texto parâmetro do OCP. Definir o início potencial de 100 mV abaixo do valor OCP gravado. Definir o potencial vértice superior a 800 mV, o vértice inferior a 100 mV abaixo do potencial de início e o potencial de paragem a 100 mV abaixo do potencial vértice inferior. Definir a taxa de digitalização para 0,001 V / seg e o potencial passo para 0,0024 V / seg. Agora pressione Start. </li></ol> 5. Após a conclusão da corrosão Run Nota: Após a finalização da corrosão executar a verificação de polarização é mostrado na vista de análise do software. Para cada polarização executar a vista do apresentador lista o OCP, a trama de E vs. t ea escadaria CV que é um terreno de E vs. Log (i). <ol><li> Dentro de cada parcela ltinta, determinar filtração interna dos pontos de dados, Tafel extrapolação, e as opções de enredo. Expandir cada ligação apresentada para mostrar vários parâmetros de interesse, que formam colectivamente os parâmetros electroquímicos. A digitalização de polarização (densidade de corrente versus potencial), determina o potencial de circuito aberto, colocando potencial (pit E) eo potencial de proteção (E pro). </li><li> Tabular os anódico e constantes Tafel catódicos, a taxa de corrosão, a corrente de corrosão, corrosão densidade de corrente, o potencial de início e fim potencial sob a taxa de corrosão através do link encosta Tafel. </li></ol> 6. retirar a amostra do suporte do eletrodo <ol><li> Prepare 3 pequenos frascos de 50 ml com diclorometano sob a coifa. </li><li> Retirar amostras testadas dos detentores dos eléctrodos por imersão da extremidade inferior do suporte em diclorometano durante 30 minutos dentro de uma fumos-capuz. </li><li> Uma vez separada, coloque o espécime para o próximo pote dediclorometano e deixar durante 15 minutos. Repita esse processo com a terceira e última lavagem para se livrar de qualquer excesso de revestimento nas secções de fixação da amostra. </li><li> Limpe o selante restante do clipe e amostra e, finalmente, enxaguar com água DI. </li></ol>

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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromium+and+cobalt+ion+concentrations+in+blood+and+serum+following+various+types+of+metal-on-metal+hip+arthroplasties:+a+literature+overview.">Chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties: a literature overview.</a> Acta Orthop. 84 (3), 229-236 (2013).</li><li>Frangini, S., De Cristofaro, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+galvanostatic+polarisation+method+for+determining+reliable+pitting+potentials+on+stainless+steels+in+crevice-free+conditions.">Analysis of galvanostatic polarisation method for determining reliable pitting potentials on stainless steels in crevice-free conditions.</a> Corros Sci. 45 (12), 2769-2786 (2002).</li></ol>

The authors have nothing to disclose.

Scans de polarização produzidos a partir de amostras de aço inoxidável mostraram parcelas contínuas limpas correlacionando com varreduras visto na literatura indicativo de um sistema de corrosão que funcione bem, que é confiável e reprodutível 29. Fraca reprodutibilidade dos potenciais picada potenciodinâmicos é identificado com um spread de algumas centenas de milivolts, com colocando ser potencial caracterizada por um processo estocástico 29. Isto é geralmente devido às variáveis ?...

técnicas electroquímicas fornecer um método rápido e relativamente barata para se obter as propriedades electroquímicas do material. Estas técnicas baseiam-se predominantemente sobre a capacidade de detectar a corrosão de um metal por observação da resposta do processo de transferência de carga para uma perturbação electroquímica controlada 1-5. A corrosão de implantes metálicos dentro de um ambiente corpo é crítica devido às implicações adversas na biocompatibilidade e material de integridade 6. O principal factor que contribui para a corrosão do implante dentro do corpo, é a dissolução do óxido de superfície conduz a um aumento da libertação de iões metálicos 7-11. Isto resulta em reacções biológicas adversas, as quais podem ser encontrados no local, mas com efeitos potencialmente sistémicos que conduzem à falha prematura do implante 10,12-28. As características de corrosão de uma amostra de ensaio são previstas a partir da verificação de polarização produzidapor um potenciostato. Uma varredura polarização permite a extrapolação dos parâmetros cinéticos e de corrosão de um substracto de metal. Durante a verificação, a oxidação ou a redução de uma espécie electro-activo pode ser limitada pela transferência de carga e o movimento dos reagentes ou dos produtos. Estes factores são todos encapsulados pela verificação de polarização; portanto, a importância de ter um sistema que produz uma varredura polarização fiável e reproduzível em vários ciclos é de grande importância. O foco principal deste artigo é o de fornecer um protocolo de identificação da lógica e as medidas tomadas para obter um sistema de corrosão potenciodinâmica que funcione bem.

<table><tbody><tr><td>Potentiostat</td><td>Metrohm</td><td>PGSTAT101</td><td></td></tr><tr><td>Ag/AgCl reference electrode, shielded</td><td>Metrohm</td><td>6.0729.100</td><td></td></tr><tr><td>Electrode shaft</td><td>Metrohm</td><td>6.1241.060</td><td></td></tr><tr><td>Polisher Forcipol 1v</td><td>Metkon</td><td>3602</td><td></td></tr><tr><td>Clindrical flask 700 ml</td><td>SciLabware</td><td>FR700F</td><td></td></tr><tr><td>Reaction lid</td><td>SciLabware</td><td>MAF2/41</td><td></td></tr><tr><td>Dichloromethane</td><td>Sigma-Aldrich</td><td>MKBR7629V</td><td>Use under a fumehood. Wear protective clothing.</td></tr><tr><td>Thermo / HAAKE D Series Immersion Circulators</td><td>Haake</td><td></td><td></td></tr></tbody></table>

potentiodynamic corrosion testing

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation potential of the material. The detection of these electrochemical parameters identifies the corrosion factors of a material. A reliable and well-functioning corrosion system is required to achieve this.
Corrosion of the samples was achieved via a potentiodynamic polarization technique employing a three-electrode configuration, consisting of reference, counter, and working electrodes. Prior to commencement a baseline potential is obtained. Following the stabilization of the corrosion potential (Ecorr), the applied potential is ramped at a slow rate in the positive direction relative to the reference electrode. The working electrode was a stainless steel screw. The reference electrode was a standard Ag/AgCl. The counter electrode used was a platinum mesh. Having a reliable and well-functioning in vitro corrosion system to test biomaterials provides an in-expensive technique that allows for the systematic characterization of the material by determining the breakdown potential, to further understand the material's response to corrosion. The goal of the protocol is to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

Na conclusão do procedimento de um sistema in vitro corrosão é configurado para realizar estudos de corrosão. Procedimentos específicos, tais como a limpeza do vaso de corrosão e a gaiola de Faraday foram introduzidas no protocolo para melhorar o desempenho do ruído. O conceito fundamental de uma boa verificação polarização é identificar as condições de electro-físico do material que proporciona informação valiosa, a fim de compreender a susceptibilidade de corr...

Watch this Scientific Journal Video about Potentiodynamic Corrosion Testing at JoVE.com

Potentiodynamic Corrosion Testing

Here, we present a protocol to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

Potenciodinâmica Corrosão Testing

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation ...

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17.5K visualizações.  Prince of Wales Clinical School. Here, we present a protocol to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices. 

Vídeo: Potentiodynamic Corrosion Testing

Metal Corrosion and the Efficiency of Corrosion Inhibitors in Less Conductive Media

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, prevent them and minimize the damages associated with them. One of the most important characteristics of corrosion processes is the corrosion rate. The measurement of corrosion rates is often very difficult or even impossible especially in less conductive, non-aqueous environments such as biofuels. Here, we present five different methods for the determination of corrosion rates and the efficiency of anti-corrosion protection in biofuels: (i) a static test, (ii) a dynamic test, (iii) a static test with a reflux cooler and electrochemical measurements (iv) in a two-electrode arrangement and (v) in a three-electrode arrangement. The static test is advantageous due to its low demands on material and instrumental equipment. The dynamic test allows for the testing of corrosion rates of metallic materials at more severe conditions. The static test with a reflux cooler allows for the testing in environments with higher viscosity (e.g., engine oils) at higher temperatures in the presence of oxidation or an inert atmosphere. The electrochemical measurements provide a more comprehensive view on corrosion processes. The presented cell geometries and arrangements (the two-electrode and three-electrode systems) make it possible to perform measurements in biofuel environments without base electrolytes that could have a negative impact on the results and load them with measurement errors. The presented methods make it possible to study the corrosion aggressiveness of an environment, the corrosion resistance of metallic materials, and the efficiency of corrosion inhibitors with representative and reproducible results. The results obtained using these methods can help to understand corrosion processes in more detail to minimize the damages caused by corrosion.

The testing of processes associated with material corrosion can often be difficult especially in non-aqueous environments. Here, we present different methods for short-term and long-term testing of corrosion behavior of non-aqueous environments such as biofuels, especially those containing bioethanol.

Corrosão do metal e a eficiência de inibidores de corrosão em meios menos condutivos

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, ...

Ambiente

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Espectroscopia de impedância eletroquímica como uma ferramenta para estimativa de constante taxa eletroquímica

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Química

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Síntese de nanofios de níquel e platina e otimização de desempenho de redução do oxigênio

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory.
Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged.
The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.

We propose a method to measure a parameter that is highly relevant for corrosion assessments or predictions of reinforced concrete structures, with the main advantage of permitting testing of samples from engineering structures. This ensures real conditions at the steel-concrete interface, which are crucial to avoid artifacts of laboratory-made samples.

Protocolo experimental para determinar o valor de limiar de cloreto para corrosão em amostras colhidas de estruturas de concreto armado

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these ...

Engenharia

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition.

This protocol describes the measurement of the electromotive force of alkaline-earth elements in liquid metal alloys at high temperatures (723-1,123 K) to determine their thermodynamic properties, including activity, partial molar entropy, partial molar enthalpy, and phase transition temperatures, over a wide composition range.

Determinação de propriedades termodinâmicas de líquidos alcalinos terrosos de ligas metálicas utilizando a técnica de força eletromotriz

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline ...

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).

Análise da aplicabilidade dos métodos de avaliação de parâmetros morfológicos das barras de aço corroídas

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly ...

Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, batteries, and biomedical devices, etc., impose great challenges on the reliable performance of alloys exposed to extreme conditions where mechanical and electrochemical attack co-exist. Finding ways for alloys to mitigate the combined attack of wear and corrosion (i.e., tribocorrosion) under such extreme conditions is thus highly critical for improving their reliability and service lifetime when used in such conditions. The challenge lies in the fact that wear and corrosion are not independent of each other, but rather work synergistically to accelerate the total material loss. Thus, a reliable method to evaluate the tribocorrosion resistance of metals and alloys is needed. Here, a protocol for measuring the tribocorrosion rate and wear-corrosion synergy of Al-based bulk and thin film samples in a corrosive environment under room temperature is presented.

Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

Determinar a taxa de Tribocorrosion e sinergia de desgaste-corrosão de ligas de alumínio de película fina e granel

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, ...

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries of the metal. Using this method, a crack free, thin-film macroelectrode surface with up to 40 times increase in active surface area was obtained. The roughening is easy to do in a standard electrochemical characterization laboratory and incudes the application of voltage pulses followed by extended application of a reductive voltage in a perchloric acid solution. The protocol includes the chemical and electrochemical preparation of both a macroscale (1.2 mm diameter) and microscale (20 &#181;m diameter) platinum disc electrode surface, roughening the electrode surface and characterizing the effects of surface roughening on electrode active surface area. This electrochemical characterization includes cyclic voltammetry and impedance spectroscopy and is demonstrated for both the macroelectrodes and the microelectrodes. Roughening increases electrode active surface area, decreases electrode impedance, increases platinum charge injection limits to those of titanium nitride electrodes of same geometry and improves substrates for adhesion of electrochemically deposited films.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

Desbaste eletroquímico de macro e microeletrodos de platina de película fina

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries ...

Applying Dynamic Strain on Thin Oxide Films Immobilized on a Pseudoelastic Nickel-Titanium Alloy

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to emerge. Tuning material structure can be achieved by controlling an external force imposed on materials and inducing stress-strain responses (i.e., applying dynamic strain). Electroactive thin films are typically deposited on shape or volume tunable elastic substrates, where mechanical loading (i.e., compression or tension) can affect film structure and function through imposed strain. Here, we summarize methods for straining n-type doped titanium dioxide (TiO2) films prepared by a thermal treatment of a pseudo-elastic nickel-titanium alloy (Nitinol). The main purpose of the described methods is to study how strain affects electrocatalytic activities of metal oxide, specifically hydrogen evolution and oxygen evolution reactions. The same system can be adapted to study the effect of strain more broadly. Strain engineering can be applied for optimization of a material function, as well as for design of adjustable, multifunctional (photo)electrocatalytic materials under external stress control.

Dynamic, tensile strain is applied on TiO2 thin films to study the effects of strain on electrocatalysis, specifically proton reduction and water oxidation. TiO2 films are prepared by thermal treatment of the pseudo-elastic NiTi alloy (Nitinol).

Aplicando tensão dinâmica em filmes de óxido fino imobilizado em uma liga pseudoelástica de níquel-titânio

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to ...

Electrochemical Measurements of Supported Catalysts Using a Potentiostat/Galvanostat

Source: Laboratory of Dr. Yuriy Rom&#225;n &#8212; Massachusetts Institute of Technology
A potentiostat/galvanostat (often referred to as simply a potentiostat) is an instrument that measures current at an applied potential (potentiostatic operation) or measures potential at an applied current (galvanostatic operation) (Figure 1). It is the most commonly used instrument in the electrochemical characterization of anode and cathode materials for fuel cells, electrolyzers, batteries, and supercapacitors.
Conventionally, these anode and cathode materials are interfaced with a potentiostat via a three-electrode electrochemical cell. The electrode leads from the potentiostat are connected to the reference electrode, the counter electrode (often called the auxiliary electrode), and the working electrode (which contains the test material of interest). The electrochemical cell is then filled with a high ionic strength electrolyte solution, such as an acidic, alkaline, or salt solution. The media for this high ionic strength solution is typically aqueous; however, for applications necessitating higher operating cell potential windows, such as batteries and supercapacitors, non-aqueous media is often used. The cell media is degassed with an inert gas (to prevent unwanted side reactions) or with a test gas (if the test reaction involves a gas at one of the electrodes).
Alternatively, a salt bridge or membrane is employed to maintain ionic contact if the two half cells are to be measured in different electrolytes. In heterogeneous electrocatalysis, this type of &#34;two compartment&#34; cell is often used if the test molecule at the working electrode is also reactive at the counterelectrode. This happens frequently as the counterelectrode typically employed is platinum, which is a highly active catalyst for many reactions. Here, single compartment cells will be used, where all three electrodes are in the same media.
This video will explain the process of polishing a working electrode, preparing a catalyst ink, mounting the catalyst ink onto the working electrode, preparing the electrochemical cell, and then performing electrochemical measurements. The measurements that are performed include: cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronopotentiometry (CP), and chronoamperometry (CA).
<img alt="Figure 1" src="/files/ftp_upload/5698/5698fig1.jpg" /> 
Figure 1. An example of a single compartment electrochemical cell. a.) Teflon cap, b.) glass cell, c.) Pt wire counter electrode, d.) working electrode, e.) Ag/AgCl reference electrode, f.) 0.5 M aqueous sulfuric acid electrolyte solution.