Electrochemical behavior of carbon steel pre-treated with an organo functional bis-silane filled with copper phthalocyanine

The bis-[trimethoxysilylpropyl]amine (BTSPA) film filled with copper phthalocyanine (Cu-Ph) was prepared by adding different concentrations of copper phthalocyanine - Cu-Ph and deposited on a carbon steel substrate using 120 ºC and 150 ºC as curing temperatures. For samples cured at 150 ºC a second layer was also deposited. The electrochemical behavior of carbon steel coated with BTSPA filled with Cu-Ph was studied by electrochemical measurements, electrochemical impedance spectroscopy (EIS) and polarization curves, in aerated 0.1 mol L-1 NaCl solution. Physical and chemical characterization was made by thermogravimetric analysis (TGA), scanning electron microscopy, contact angle measurements and infrared spectroscopy. TGA showed no decomposition of Cu-Ph during the curing process. Cu-Ph added into the silane film showed a strong influence on its corrosion resistance, mainly when the samples are cured at 150 ºC. The results showed that lower inhibitor concentrations led to a higher corrosion resistance and the second layer increased by one order of magnitude the corrosion resistance.Neste trabalho, depositou-se sobre aço carbono o filme de bis-[trimetoxisililpropil]amina (BTSPA) adicionado de ftalocianina de cobre (Cu-Ph). Na obtenção desse filme variou-se as concentrações de Cu-Ph e a temperatura de cura (120 e 150 °C) e nas amostras curadas à 150°C, adicionou-se uma segunda camada. O comportamento eletroquímico do aço carbono recoberto com o filme aditivado com Cu-Ph foi estudado por técnicas eletroquímicas (medidas de espectroscopia de impedância eletroquímica e curvas de polarização) em solução aerada de NaCl 0,1 mol L-1. A caracterização física e química foi feita por análise termogravimétrica (TGA), microscopia eletrônica de varredura, medidas de ângulo de contato e espectroscopia de infravermelho. A TGA não mostrou decomposição da Cu-Ph durante o processo de cura e a quantidade de Cu-Ph adicionada ao filme polissilânico apresentou forte influência na resistência à corrosão, principalmente quando a amostra é curada a 150 °C. Os resultados mostraram que menores concentrações de inibidor forneceram maior resistência à corrosão e a segunda camada aumentou em uma ordem de grandeza a resistência à corrosão.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

In vitro evaluation of the erosive potential of orange juice modified by food additives in enamel and dentine

AbstractObjectivesTo evaluate the erosive potential of orange juice modified by food additives in enamel and dentine.MethodsCalcium lactate pentahydrate (CLP), xanthan gum (XG), sodium linear polyphosphate (LPP), sodium pyrophosphate tetrabasic (PP), sodium tripolyphosphate (STP) and some of their combinations were added to an orange juice. Pure orange juice and a calcium-modified juice were used as negative (C−) and positive (C+) controls, respectively. In phase 1, 15 modified orange juices were tested for erosive potential using pH-stat analysis. In phase 2, the additives alone and the combination with good results in phase 1 and in previous studies (CLP+LPP) were tested in an erosion–remineralization cycling model. In phase 3, the erosion and remineralization episodes were studied independently. Enamel was analysed by surface microhardness (SMH) and profilometry, whilst dentine by profilometry.ResultsIn phase 1, reduction of the erosive potential was observed for all additives and their combinations, except XG alone. In phase 2, no detectable enamel loss was observed when CLP, LPP and CLP+LPP were added to the juice. XG, STP and PP had enamel loss similar to C− (p>0.05). Amongst additives, the combination CLP+LPP showed the highest SMH values followed by CLP (p<0.05). All the other groups presented SMH values similar to C− (p>0.05). For dentine, only CLP+LPP lead to surface loss values lower than C− (p<0.05). In phase 3, CLP, LPP and CLP+LPP seemed to protect against erosion; whilst none of the tested compounds seemed to interfere with the remineralization process.ConclusionsCLP and LPP reduced erosion on enamel and this effect was enhanced by their combination. For dentine, only the combination CLP+LPP reduced erosion

Supplementation of an Orange Juice with Dietary Proteins to Prevent Enamel and Dentin Erosion

Protein supplementation may be an alternative to reduce the erosive potential of acidic drinks. The aim of this in vitro study was to evaluate the erosive potential of an orange juice modified by dietary proteins. A commercially available orange juice was added 0.2 g/L casein, 2.0 g/L ovalbumin and their combination. The juice with no additives and a commercially available calcium-modified juice were used as negative and positive controls, respectively. Human enamel and dentin specimens (n=11) were tested in an erosion-remineralization cycling model. Enamel was analyzed by surface microhardness and profilometry, whilst dentin by profilometry only. Statistical analyses were performed using one-way ANOVA followed by Tukey's test (p<0.05). Calcium-modified juice showed the lowest erosive potential for both analyses (p<0.05). For enamel, the protein-added groups did not differ from each other (p>0.05) and showed significantly lower enamel loss compared to negative control (p<0.05). Regarding surface microhardness, casein showed the highest values compared to negative control (p<0.05). For dentin, none of the protein-added groups showed lower values of surface loss compared to negative control (p>0.05). In conclusion, for enamel the protein-modified orange juices presented reduced erosion of enamel, with casein showing a trend for better protection. For dentin, no reduction in the erosive potential was observed for the tested protein-modified orange juices

Microstructural and electrochemical characterization of environmentally friendly conversion layers on aluminium alloys

Cerium conversion layers (CeCL) have been investigated as a replacement for chromium conversion layers to protect Al alloys against corrosion. In this work the microstructure and the electrochemical behaviour of aluminium alloy 2024 with and without CeCL were investigated using, respectively, SEM-EDX and EIS. EDX results have shown that the presence of dispersed plated Cu particles on the alloy surface enhances the formation of the CeCL increasing the intensity of Ce peaks in the EDX spectra. EIS measurements on conversion-coated samples have shown that the presence of the layer increases the impedance, and that its presence is detected by the presence of a high frequency time constant. Results of potentiodynamic experiments have shown that the corrosion protection afforded by the conversion layer is due to the hindrance of the oxygen reduction reaction and that the pitting potential of the alloy is not changed

Electrochemical study of modified non-functional bis-silane layers on Al alloy 2024-T3

In the last few years great efforts have been made in order to find and to develop environmentally friendly substitutes for Cr6+ pre-treatments applied on aluminium alloys used in the aircraft industry. Among the potential substitutes, silane layers have attracted considerable interest from researchers and from the industry. The present work investigates the anti-corrosion behaviour of (bis-1, 2-(triethoxysilyl) ethane (BTSE)) silane layers modified with Ce ions and/or silica nanoparticles applied on Al alloy 2024-T3 substrates. The corrosion behaviour was investigated in 0.1 M NaCl solution via d.c. polarization and electrochemical impedance spectroscopy (EIS). Contact angle measurements and XPS were used to assess information on the chemistry of the silane pre-treated surfaces. The results have shown that the introduction of additives improves the corrosion protection properties of the silane layer. (c) 2008 Elsevier Ltd. All rights reserved

Microstructural and electrochemical characterization of environmentally friendly conversion layers on aluminium alloys

Cerium conversion layers (CeCL) have been investigated as a replacement for chromium conversion layers to protect Al alloys against corrosion. In this work the microstructure and the electrochemical behaviour of aluminium alloy 2024 with and without CeCL were investigated using, respectively, SEM-EDX and EIS. EDX results have shown that the presence of dispersed plated Cu particles on the alloy surface enhances the formation of the CeCL increasing the intensity of Ce peaks in the EDX spectra. EIS measurements on conversion-coated samples have shown that the presence of the layer increases the impedance, and that its presence is detected by the presence of a high frequency time constant. Results of potentiodynamic experiments have shown that the corrosion protection afforded by the conversion layer is due to the hindrance of the oxygen reduction reaction and that the pitting potential of the alloy is not changed

Anti-erosive properties of solutions containing fluoride and different film-forming agents

Objectives: To evaluate the anti-erosive potential of solutions containing sodium fluoride (NaF, 225 ppm F) and different film-forming agents.Methods: In Phase 1, hydroxyapatite crystals were pre-treated with solutions containing NaF (F), linear sodium polyphosphate (LPP), sodium pyrophosphate tetrabasic (PP), sodium tripolyphosphate (STP), sodium caseinate (SC), bovine serum albumin (BSA), stannous chloride (Sn) and some combinations thereof. Deionized water was the control (C). The pH-stat method was used to evaluate hydroxyapatite dissolution. In Phase 2, the most effective solutions were tested in two independent experiments. Both consisted of an erosion-remineralization cycling model using enamel and dentine specimens with three solution treatments per day. In Phase 2a, the challenge was performed with 0.3% citric acid (pH = 3.8). In Phase 2b, 1% citric acid (pH = 2.4) was used. Hard tissue surface loss was determined profilometrically. Data were analyzed with two-way ANOVA and Tukey tests.Results: In Phase 1, F, LPP, Sn and some of their combinations caused the greatest reduction in hydroxyapatite dissolution. In Phase 2a, C showed the highest enamel loss, followed by LPP. There were no differences between all other groups. In Phase 2b: (F + LPP + Sn) &lt; (F + LPP) = (F + Sn) &lt; (F) = (LPP + Sn) &lt; (LPP) &lt; (Sn) &lt; C. For dentine, in both experiments, only the fluoride-containing groups showed lower surface loss than C, except for LPP + Sn in 2a.Conclusions: F, Sn, LPP reduced enamel erosion, this effect was enhanced by their combination under highly erosive conditions. For dentine, the F-containing groups showed similar protective effect.Clinical significance: The addition of LPP and/or Sn can improve the fluoride solution protection against erosion of enamel but not of dentine. (C) 2015 Elsevier Ltd. All rights reserved

Electrochemical study of modified cerium-silane bi-layer on Al alloy 2024-T3

In this paper, the performance of bis-1, 2-(triethoxysilyl) ethane (BTSE) as a pre-treatment to protect the AA 2024-T3 against corrosion has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves, and the scanning vibrating electrode technique (SVET). The microstructural and morphological characterizations were carried out via scanning electron microscopy and atomic force microscopy and the chemical composition evaluated using contact angle measurements and X-ray photoelectron spectroscopy (XPS). The electrochemical results showed that the additives improved the anticorrosion properties of the coating. The chemical characterization indicated that additives contribute to an increased degree of surface coverage, as well as to a more complete reticulation. The SVET results evidenced the self-healing abilities of Ce ions. (C) 2009 Elsevier Ltd. All rights reserved.FAPESPCNP

Anti-Erosive Effect of Solutions Containing Sodium Fluoride, Stannous Chloride, and Selected Film-Forming Polymers

The aim of this study was to evaluate the anti-erosive effect of solutions containing sodium fluoride (F: 225 ppm F-), stannous chloride (Sn: 800 ppm Sn2+), and some film-forming polymers (Gantrez: Poly [methylvinylether-alt-maleic anhydride]; PGA: propylene glycol alginate; Plasdone: poly[vinylpyrrolidone]; and CMC: carboxymethylcellulose). Solutions were tested in an erosion-remineralization cycling model, using enamel and dentin specimens (n = 10, for each substrate). Distilled water was the negative control. Cycling consisted of 120 min immersion in human saliva, 5 min in 0.3% citric acid solution, and 120 min of exposure to human saliva, 4×/day, for 5 days. Treatment with solutions (pH = 4.5) was carried out 2×/day, for 2 min. Surface loss (SL) was evaluated with optical profilometry. Zeta potential of hydroxyapatite crystals was determined after treatment with the solutions. Data were statistically analyzed (α = 0.05). For enamel, all polymers showed significantly lower SL (in µm) than the control (11.09 ± 0.94), except PGA (10.15 ± 1.25). PGA significantly improved the protective effect of F (4.24 ± 0.97 vs. 5.64 ± 1.60, respectively). None of the polymers increased the protection of F+Sn (5.13 ± 0.78). For dentin, only Gantrez (11.40 ± 0.97) significantly reduced SL when compared with the negative control (12.76 ± 0.75). No polymer was able to enhance the effect of F (6.28 ± 1.90) or F+Sn (7.21 ± 1.13). All fluoridated solutions demonstrated significantly lower SL values than the control for both substrates. Treatment of hydroxyapatite nanoparticles with all solutions resulted in more negative zeta potentials than those of the control, except Plasdone, PGA, and F+Sn+PGA, the latter two presenting the opposite effect. In conclusion, Gantrez, Plasdone, and CMC exhibited an anti-erosive effect on enamel. PGA increased the protection of F. For dentin, only Gantrez reduced erosion