Compositional and structural changes at the anodic surface of thermally poled soda-lime float glass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of spraying parameters on the electrochemical behaviour of HVOF thermally sprayed stainless steel coatings in 3.4% NaCl

Stainless steel coatings obtained by High Velocity Oxygen Fuel (HVOF) were characterized using optical (OM) and scanning electron microscopy (SEM), electron probe micro-analysis, X-ray diffraction (XRD), open-circuit potential (E-OC) measurements, electrochemical impedance spectroscopy (EIS) and polarisation tests. Differences among coated steels were mainly related with the gun-substrate distance parameter (310 nm for samples A and B and 260 min for C and D). The open-circuit potential values measured for all the samples after 18 h of immersion in aerated and unstirred 3.4% NaCl solution were: - 0.334, - 0.360, - 0.379 and - 0.412 V vs. Ag/AgCl,KClsat. for samples A to D, respectively. For EIS measurements, Nyquist plots showed higher capacitive semi-circle for samples sprayed at longer distance, indicating higher corrosion resistance in NaCl solution. (c) 2005 Elsevier B.V. All rights reserved.

The influence of gun transverse speed on electrochemical behaviour of thermally sprayed Cr3C2-NiCr coatings in 0.5 M H2SO4 solution

In the present study, different types of 75% Cr3C2-25% NiCr coatings were applied on a steel substrate by means of high velocity oxygen fuel spraying (HVOF), and studied using ac and dc electrochemical measurements in an aerated and unstirred 0.5 M H2SO4 solution. Structural characterization was determined before and after electrochemical tests. Differences between all sprayed systems are related to the gun transverse speed and number of deposited layers, which strongly affected the electrochemical characteristics of the coated steels. The coating obtained with a higher torch speed showed better resistance against corrosion. The electrochemical impedance results were analyzed using an equivalent circuit where porosity of the coatings and substrate oxidation were considered. (C) 2003 Elsevier Ltd. All rights reserved.

Electrochemical behavior of thermally sprayed stainless steel coatings in 3.4% NaCl solution

Four types of stainless steel coatings prepared by a high velocity oxy-fuel spraying system (HVOF) were studied. Differences among coated steels were related to the spraying parameters, which influenced the behavior of the samples against the corrosion. The electrochemical behavior of the stainless steel coatings was strongly influenced by porosity, the presence of micro- and macro-cracks, and also of un-melted particles. Once the electrolyte reached the steel substrate via these defects, the galvanic pair formed between the coating and substrate-accelerated corrosion, leading to the depletion of the coating. (C) 2004 Elsevier Ltd. All rights reserved.

Electrochemical behaviour of thermally sprayed Cr3C2-NiCr coatings in 0.5 M H2SO4 media

The electrochemical behaviour of coated Cr3C2-NiCr steel in aerated 0.5 M H2SO4 solution was studied by means of electrochemical a.c. and d.c. measurements. A complete structural characterization of the coated steel before and after electrochemical tests was also carried out to access the corrosion mechanism of coated steel, electrolyte penetration through the coating, and to confirm the results obtained using electrochemical techniques. Two types of Cr3C2-NiCr coatings produced by a high velocity oxy-fuel spraying system (HVOF) were studied. Differences between coated steels are related to the spraying parameters reflecting their behaviour against corrosion phenomena. The electrochemical behaviour of the coated steel was strongly influenced by porosity and the presence of microcracks in the coating. Once the electrolyte reaches the steel substrate, it corrodes in a galvanic manner resulting in coating detachment from the steel.

Al3+ environments in nanostructured ZnAl2O4 and their effects on the luminescence properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)