En este estudio se presenta el decapado del acero inoxidable austenítico 316L utilizando mezclas ... more En este estudio se presenta el decapado del acero inoxidable austenítico 316L utilizando mezclas de peróxido de hidrógeno (H 2 O 2)/ácido sulfúrico (H 2 SO 4)/iones fluoruro; los iones fluoruro provienen del ácido fluorhídrico (HF), fluoruro de sodio (NaF) y fluoruro de potasio (KF). La estabilidad del H 2 O 2 fue valorada modificando las concentraciones del ión férrico de 0 a 40 g/l y las temperaturas de 25 °C a 60 °C en las mezclas decapantes. Se establecieron las condiciones óptimas de decapado utilizando 20 g/l de iones férrico a 25 °C empleando el ácido p-toluensulfónico como estabilizante del H 2 O 2. La mezcla que contenía HF fue la única capaz de eliminar completamente los óxidos superficiales del acero a tiempos de 300 s. Las mezclas a base de sales fluoradas eliminaron parcialmente los óxidos (20 y 40 % aprox.) en 300 s. Al incrementar el tiempo de decapado hasta 1200 s se obtuvieron porcentajes de eliminación alrededor de un 80 %. Palabras clave Acero inoxidable; Mezclas decapantes ecológicas; Óxidos de hierro; Peróxido de hidrógeno; Ácido fluorhídrico; Sales fluoradas.
RESUMEN: Con objeto de mejorar la resistencia a la corrosión de implantes biodegradables de magne... more RESUMEN: Con objeto de mejorar la resistencia a la corrosión de implantes biodegradables de magnesio y de la aleación AZ31, se ha depositado un recubrimiento de ácido fítico sobre ambos sustratos y se ha evaluado su efecto protector frente a la corrosión. El recubrimiento fue obtenido mediante un tratamiento de conversión química, por inmersión en una solución de ácido fítico al 0,5% a 60 °C. Distintas técnicas (MEB/EDX, XRD y FTIR) fueron utilizadas para analizar la morfología del recubrimiento y su naturaleza química. Dichas técnicas mostraron que el recubrimiento de conversión era amorfo, con una composición química sobre la superficie de magnesio de Mg, O y P y, además, Al, Zn y C sobre la superficie de la aleación AZ31. Los componentes principales del recubrimiento fueron quelatos formados por ácido fítico e iones metálicos. La resistencia a la corrosión de muestras sin recubrir y recubiertas, se evaluó mediante polarización potenciodinámica en solución de Hank a 37 °C. Los resultados indican que los recubrimientos de conversión de ácido fítico proporcionan una protección muy efectiva a los substratos de magnesio estudiados.
h i g h l i g h t s Mechanical and chemical methods are employed for recycle waste PET. PET recyc... more h i g h l i g h t s Mechanical and chemical methods are employed for recycle waste PET. PET recycled resin with similar properties to commercial resin is obtained. PET recycled resin is used as joint material between PET particles and sand. Polymer mortars with acceptable physical and mechanics proprieties are obtained.
The corrosion protection provided by an organic inhibitor containing an alkanolamine salt of a po... more The corrosion protection provided by an organic inhibitor containing an alkanolamine salt of a polycarboxilic acid that is suggested as non-toxic alternative to chromate and phosphate conversion coatings on galvanized steel was studied. Open circuit corrosion potential evolution, ...
This work attempts to determine the best conditions for applying the Electrochemical Chloride Rem... more This work attempts to determine the best conditions for applying the Electrochemical Chloride Removal (ECR) in rebars embedded in cement mortar with chloride additions by monitoring the corrosion rates before, during and after the application of an ECR. The ECR was applied at different conditions of current density (1 and 2 A/m 2 of steel surface), application times (15, 30 and 60 days) and degree of precorrosion of the rebars. According to the results obtained, if ECR is applied preventively, it is an efficient procedure for delaying the start of corrosion. However, if applied too late, it does not assure the repassivation of corroded reinforced concrete structures and is therefore useless. The efficiency of the ECR depends heavily on the application time and the degree of precorrosion of the rebars.
Comportamiento del acero precorroído en solución saturada de Ca(OH) 2 y en mortero de cemento. Po... more Comportamiento del acero precorroído en solución saturada de Ca(OH) 2 y en mortero de cemento. Posibilidades de rehabilitación
Estabilidad del estado pasivo del acero en morteros de ceniza volante activada Steel passive stat... more Estabilidad del estado pasivo del acero en morteros de ceniza volante activada Steel passive state stability in activated fly ash mortars
The corrosion rate of steel in reinforced concrete structures may be estimated from the potential... more The corrosion rate of steel in reinforced concrete structures may be estimated from the potential decay curve after a pulse interruption, provided that the steel surface area intervening in the measurements is known. Considering that the time constant (τ) of the corrosion process is independent of the surface area, it is also possible to determine the corrosion rate from direct measurements of τ without the need to know the rebar surface area, provided that the double-layer capacitance value is previously known or a reasonable value of this variable is assumed. The method may also be applied in realsized structures, using small, easy-to-use counter electrodes. Experiments have been performed using small mortar specimens (8.0 cm by 5.5 cm by 2.0 cm) and larger-sized slabs (90 cm by 65 cm by 10 cm) simulating real structures. Rebars were embedded in concrete with and without additives (chlorides and nitrites) and with a cement/sand/water ratio of 1/3/0.5. The reliability of the data obtained is comparable to that of generally accepted conventional electrochemical procedures for measuring linear polarization resistance.
In situ measurements of steel corrosion rate in large reinforced concrete structures face difficu... more In situ measurements of steel corrosion rate in large reinforced concrete structures face difficulties of different types. The paper discusses some of the problems connected with the determination of the true value of the polarisation resistance from (i) the time constant value associated with the corrosion process, and (ii) the use of a guard ring for confining the electrical signal to a definite reinforcement area. In (i), results corroborate the assumption of a time constant value independent of the area affected by the electrical signal, albeit with some exceptions. In (ii), it is shown the great importance of achieving a critical ratio between the current intensities that flow from the guard ring and counter-electrode.
The question of whether reinforcing steel can be protected with activated fly ash cement as effec... more The question of whether reinforcing steel can be protected with activated fly ash cement as effectively as with Portland cement is explored in this study. Corrosion potential (E corr) and polarisation resistance (R p) values for steel electrodes embedded in Portland cement mortar and two fly ash mortars, respectively activated with NaOH and waterglass+NaOH solutions, are monitored. Chloride-free activated fly ash mortars are found to passivate steel reinforcement as speedily and effectively as Portland cement mortars, giving no cause to fear that corrosion may limit the durability of reinforced concrete structures built with these new types of activated fly ash cement. The polarisation curves and the response to short-term anodic current pulses (galvanostatic pulse technique) obtained further corroborate the full and stable passivation of the steel by the concrete manufactured with these binders.
Abstract In this study, corrosion products on steel reinforcing bars (rebars) exposed in mortar c... more Abstract In this study, corrosion products on steel reinforcing bars (rebars) exposed in mortar contaminated with chlorides were characterised. For this purpose, scanning electron images were taken on steel surface and energy dispersive spectrometry analyses, as well X-ray diffraction was employed for quantitative characterisation using the Rietveld method. The main phases present were maghemite, goethite, lepidocrocite and akaganeite. Dans cette étude, on a caractérisé les produits de corrosion de barres de renforcement en acier (barres d’armature) exposées dans du mortier contaminé par des chlorures. À cette fin, on a pris des images au microscope électronique à balayage, à la surface de l’acier, et l’on a employé des analyses de spectroscopie à dispersion d’énergie ainsi que la diffraction des rayons X pour la caractérisation quantitative, en utilisant la méthode de Rietveld. Les principales phases présentes consistaient en maghémite, en goéthite, en lépidocrocite et en akaganéite.
PurposeThe purpose of this paper is to investigate corrosion protection provided by a water‐solub... more PurposeThe purpose of this paper is to investigate corrosion protection provided by a water‐soluble corrosion inhibitor as a non‐toxic alternative to the chromate and phosphate conversion coatings on galvanised steel.Design/methodology/approachUntreated galvanised steel samples were assessed simultaneously with galvanised steel samples treated with the chromate‐free organic inhibitor, a conventional chromate conversion coating or a zinc phosphate modified with nickel, by means of immersion – weigh loss and electrochemical tests, using a naturally aerated 0.5 M NaCl aqueous solution as corrosive medium. In addition, selected superficial conditions of galvanised steel were submitted to a salt fog test. The electrochemical tests used were: open circuit corrosion potential logging, linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy. Corrosion products formed on samples withdrawn from the solution at different intervals were characterized using X...
En este estudio se presenta el decapado del acero inoxidable austenítico 316L utilizando mezclas ... more En este estudio se presenta el decapado del acero inoxidable austenítico 316L utilizando mezclas de peróxido de hidrógeno (H 2 O 2)/ácido sulfúrico (H 2 SO 4)/iones fluoruro; los iones fluoruro provienen del ácido fluorhídrico (HF), fluoruro de sodio (NaF) y fluoruro de potasio (KF). La estabilidad del H 2 O 2 fue valorada modificando las concentraciones del ión férrico de 0 a 40 g/l y las temperaturas de 25 °C a 60 °C en las mezclas decapantes. Se establecieron las condiciones óptimas de decapado utilizando 20 g/l de iones férrico a 25 °C empleando el ácido p-toluensulfónico como estabilizante del H 2 O 2. La mezcla que contenía HF fue la única capaz de eliminar completamente los óxidos superficiales del acero a tiempos de 300 s. Las mezclas a base de sales fluoradas eliminaron parcialmente los óxidos (20 y 40 % aprox.) en 300 s. Al incrementar el tiempo de decapado hasta 1200 s se obtuvieron porcentajes de eliminación alrededor de un 80 %. Palabras clave Acero inoxidable; Mezclas decapantes ecológicas; Óxidos de hierro; Peróxido de hidrógeno; Ácido fluorhídrico; Sales fluoradas.
RESUMEN: Con objeto de mejorar la resistencia a la corrosión de implantes biodegradables de magne... more RESUMEN: Con objeto de mejorar la resistencia a la corrosión de implantes biodegradables de magnesio y de la aleación AZ31, se ha depositado un recubrimiento de ácido fítico sobre ambos sustratos y se ha evaluado su efecto protector frente a la corrosión. El recubrimiento fue obtenido mediante un tratamiento de conversión química, por inmersión en una solución de ácido fítico al 0,5% a 60 °C. Distintas técnicas (MEB/EDX, XRD y FTIR) fueron utilizadas para analizar la morfología del recubrimiento y su naturaleza química. Dichas técnicas mostraron que el recubrimiento de conversión era amorfo, con una composición química sobre la superficie de magnesio de Mg, O y P y, además, Al, Zn y C sobre la superficie de la aleación AZ31. Los componentes principales del recubrimiento fueron quelatos formados por ácido fítico e iones metálicos. La resistencia a la corrosión de muestras sin recubrir y recubiertas, se evaluó mediante polarización potenciodinámica en solución de Hank a 37 °C. Los resultados indican que los recubrimientos de conversión de ácido fítico proporcionan una protección muy efectiva a los substratos de magnesio estudiados.
h i g h l i g h t s Mechanical and chemical methods are employed for recycle waste PET. PET recyc... more h i g h l i g h t s Mechanical and chemical methods are employed for recycle waste PET. PET recycled resin with similar properties to commercial resin is obtained. PET recycled resin is used as joint material between PET particles and sand. Polymer mortars with acceptable physical and mechanics proprieties are obtained.
The corrosion protection provided by an organic inhibitor containing an alkanolamine salt of a po... more The corrosion protection provided by an organic inhibitor containing an alkanolamine salt of a polycarboxilic acid that is suggested as non-toxic alternative to chromate and phosphate conversion coatings on galvanized steel was studied. Open circuit corrosion potential evolution, ...
This work attempts to determine the best conditions for applying the Electrochemical Chloride Rem... more This work attempts to determine the best conditions for applying the Electrochemical Chloride Removal (ECR) in rebars embedded in cement mortar with chloride additions by monitoring the corrosion rates before, during and after the application of an ECR. The ECR was applied at different conditions of current density (1 and 2 A/m 2 of steel surface), application times (15, 30 and 60 days) and degree of precorrosion of the rebars. According to the results obtained, if ECR is applied preventively, it is an efficient procedure for delaying the start of corrosion. However, if applied too late, it does not assure the repassivation of corroded reinforced concrete structures and is therefore useless. The efficiency of the ECR depends heavily on the application time and the degree of precorrosion of the rebars.
Comportamiento del acero precorroído en solución saturada de Ca(OH) 2 y en mortero de cemento. Po... more Comportamiento del acero precorroído en solución saturada de Ca(OH) 2 y en mortero de cemento. Posibilidades de rehabilitación
Estabilidad del estado pasivo del acero en morteros de ceniza volante activada Steel passive stat... more Estabilidad del estado pasivo del acero en morteros de ceniza volante activada Steel passive state stability in activated fly ash mortars
The corrosion rate of steel in reinforced concrete structures may be estimated from the potential... more The corrosion rate of steel in reinforced concrete structures may be estimated from the potential decay curve after a pulse interruption, provided that the steel surface area intervening in the measurements is known. Considering that the time constant (τ) of the corrosion process is independent of the surface area, it is also possible to determine the corrosion rate from direct measurements of τ without the need to know the rebar surface area, provided that the double-layer capacitance value is previously known or a reasonable value of this variable is assumed. The method may also be applied in realsized structures, using small, easy-to-use counter electrodes. Experiments have been performed using small mortar specimens (8.0 cm by 5.5 cm by 2.0 cm) and larger-sized slabs (90 cm by 65 cm by 10 cm) simulating real structures. Rebars were embedded in concrete with and without additives (chlorides and nitrites) and with a cement/sand/water ratio of 1/3/0.5. The reliability of the data obtained is comparable to that of generally accepted conventional electrochemical procedures for measuring linear polarization resistance.
In situ measurements of steel corrosion rate in large reinforced concrete structures face difficu... more In situ measurements of steel corrosion rate in large reinforced concrete structures face difficulties of different types. The paper discusses some of the problems connected with the determination of the true value of the polarisation resistance from (i) the time constant value associated with the corrosion process, and (ii) the use of a guard ring for confining the electrical signal to a definite reinforcement area. In (i), results corroborate the assumption of a time constant value independent of the area affected by the electrical signal, albeit with some exceptions. In (ii), it is shown the great importance of achieving a critical ratio between the current intensities that flow from the guard ring and counter-electrode.
The question of whether reinforcing steel can be protected with activated fly ash cement as effec... more The question of whether reinforcing steel can be protected with activated fly ash cement as effectively as with Portland cement is explored in this study. Corrosion potential (E corr) and polarisation resistance (R p) values for steel electrodes embedded in Portland cement mortar and two fly ash mortars, respectively activated with NaOH and waterglass+NaOH solutions, are monitored. Chloride-free activated fly ash mortars are found to passivate steel reinforcement as speedily and effectively as Portland cement mortars, giving no cause to fear that corrosion may limit the durability of reinforced concrete structures built with these new types of activated fly ash cement. The polarisation curves and the response to short-term anodic current pulses (galvanostatic pulse technique) obtained further corroborate the full and stable passivation of the steel by the concrete manufactured with these binders.
Abstract In this study, corrosion products on steel reinforcing bars (rebars) exposed in mortar c... more Abstract In this study, corrosion products on steel reinforcing bars (rebars) exposed in mortar contaminated with chlorides were characterised. For this purpose, scanning electron images were taken on steel surface and energy dispersive spectrometry analyses, as well X-ray diffraction was employed for quantitative characterisation using the Rietveld method. The main phases present were maghemite, goethite, lepidocrocite and akaganeite. Dans cette étude, on a caractérisé les produits de corrosion de barres de renforcement en acier (barres d’armature) exposées dans du mortier contaminé par des chlorures. À cette fin, on a pris des images au microscope électronique à balayage, à la surface de l’acier, et l’on a employé des analyses de spectroscopie à dispersion d’énergie ainsi que la diffraction des rayons X pour la caractérisation quantitative, en utilisant la méthode de Rietveld. Les principales phases présentes consistaient en maghémite, en goéthite, en lépidocrocite et en akaganéite.
PurposeThe purpose of this paper is to investigate corrosion protection provided by a water‐solub... more PurposeThe purpose of this paper is to investigate corrosion protection provided by a water‐soluble corrosion inhibitor as a non‐toxic alternative to the chromate and phosphate conversion coatings on galvanised steel.Design/methodology/approachUntreated galvanised steel samples were assessed simultaneously with galvanised steel samples treated with the chromate‐free organic inhibitor, a conventional chromate conversion coating or a zinc phosphate modified with nickel, by means of immersion – weigh loss and electrochemical tests, using a naturally aerated 0.5 M NaCl aqueous solution as corrosive medium. In addition, selected superficial conditions of galvanised steel were submitted to a salt fog test. The electrochemical tests used were: open circuit corrosion potential logging, linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy. Corrosion products formed on samples withdrawn from the solution at different intervals were characterized using X...
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