Adherence measurements and corrosion resistance in primer/hot-dip galvanized steel systems

This paper focuses on the adherence during ageing of a primer (made of polyester resins crosslinked with melamine) applied onto hot-dip galvanized (HDG) steel for coil coating application and its influence on corrosion protection. A chromium-free surface treatment, composed of fluorotitanic acid, phosphoric acid, manganese phosphate, and vinylphenol was applied on the HDG steel to obtain high corrosion resistance and high adherence of a polyester and melamine primer. The influence of the manganese phosphate on the corrosion and adherence was investigated. To measure the adherence between the metal and the primer, a three-point flexure test was set up. The adherence was then linked with corrosion resistance during ageing, using electrochemical impedance spectroscopy

Корозиона стабилност превлака Zn-Mn легура добијених електрохемијским путем

Zinc alloy coatings electrochemically deposited on steel from electrolytes with different components differ in their composition, homogeneity, porosity, structure and other characteristics that affect their corrosion resistance. Manganese is characterized by a very negative electrochemical potential and very high strength, prompting many researchers to study Zn-Mn alloys for the anti-corrosion purposes in the industry, especially automotive. In this work it was examined the influence of the type of the electrolyte deposition on the current efficiency during electrodeposition of Zn-Mn alloys. Zn-Mn alloys were deposited on steel from chloride, sulphate and pyrophosphate plating baths at different current densities. We have examined the influence of deposition current density on the current efficiency during electrodeposition, appearance of alloy coatings, as well as their corrosion stability. It was shown that Zn-Mn alloys with the best corrosion properties, among all examined ones, were obtained from chloride plating bath at 2 A dm-2.Превлаке легура цинка електрохемијски добијене из електролита са различитим компонентама имају разлике у свом саставу, хомогености, порозности, структури и другим карактеристикама које утичу на њихову корозиону отпорност. Манган се одликује јако негативним електрохемијским потенцијалом и јако великом чврстоћом, што је навело многе истраживаче на испитивања легуре Zn-Mn у антикорозионе сврхе, за потребе у индустрији, нарочито аутомобилској. У овом раду испитиван је утицај врсте електролита на таложење Zn-Mn легура, као и на искоришћење струје приликом електрохемијског таложења. Легуре су таложене на челику из хлоридног, сулфатног и пирофосфатног електролита различитим густинама струје. При задатим условима таложења испитиван је хемијски састав, храпавост, изглед превлака легура, и њиховa корозиона стабилност. Показано је да највећу корозиону стабилност имају легуре добијене таложењем из хлоридног електролита густином струје од 2 A dm-2

The influence of Ce-based coatings as pretreatments on corrosion stability of top powder polyester coating on AA6060

Cerium-based conversion coatings (CeCCs) are one of the most prospective alternatives to the widely used chromate conversion coatings (CCCs) due to their anticorrosion efficiency, environmentally friendly nature and low cost. In this work, the CeCCs on AA6060 were prepared by immersion into aqueous cerium salt solutions at room temperature, and subsequently post-treated in heated phosphate solution. The effect of counter ion (nitrate and chloride) on the coating properties was studied testing CeCCs as sole or conversion layers for the top polyester coating. Since the 60 mu m thick polyester coating was applied, an artificial defect of 0.8 mm hole was introduced to faster assess the differences between pretreatments. The system with CCC pretreatment was used as reference. Corrosion properties were investigated in 0.5 M NaCl solution by electrochemical impedance spectroscopy while the adhesion strength was measured by NMPR (N-methyl-2-pyrrolidone) and pull-off tests. As shown, the post-treated chloride-based CeCC offered better protection than crack-free thin nitrate-based CeCC, when used as sole coatings. On the other hand, it was brought to evidence that in combination with top powder polyester coating, the CeCC deposited from nitrate solution exhibited better protection compared to protective system pretreated with chloride-based one. Excellent polyester coating adhesion was found independently on aluminium surface pretreatment. (C) 2013 Elsevier B.V. All rights reserved

Cerium Oxide as Conversion Coating for the Corrosion Protection of Aluminum

CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO3)(4). The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to 0.03% NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM). EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.International Conference ModTech Proceedings, 16th International Conference on Modern Technologies, Quality and Innovation, May 24-26, 2012, Sinaia, Romani

Cerium Oxide as Conversion Coating for the Corrosion Protection of Aluminum

CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO3)(4). The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to 0.03% NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM). EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.International Conference ModTech Proceedings, 16th International Conference on Modern Technologies, Quality and Innovation, May 24-26, 2012, Sinaia, Romani

Cerium Oxide as Conversion Coating for the Corrosion Protection of Aluminum

CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO3)(4). The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to 0.03% NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM). EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.International Conference ModTech Proceedings, 16th International Conference on Modern Technologies, Quality and Innovation, May 24-26, 2012, Sinaia, Romani

Characterizing the dead time of the ECLAIRs camera on board the mission SVOM

International audienceFrench (CNES) and Chinese (CNSA) space agencies collaborate to build the SVOM (Space-based multi-band Variable Object Monitor) mission due to be launched in 2021 to study gamma-ray bursts and high-energy transients. The SVOM prime instrument, ECLAIRs, will detect and localize GRBs autonomously as well as provide a spectral and temporal characterization of the GRB prompt emission. ECLAIRs is expected to detect around 200 GRBs during the 3 year nominal lifetime of the mission. ECLAIRs is a wide-field (∼ 2 {sr}) coded mask camera with a detection plane made of 8 independent sectors of 800 Schottky CdTe detectors working in the 4-150 keV energy range. Each sector is connected to independent readout electronics. In this paper, we focus on the study of the temporal performance and we estimate how dead time will affect bright transient lightcurves. We discuss the analytical model based on simulations over a large range of source count rates on a dedicated test bench. We show that dead time will not significantly affect ECLAIRs data, even for the brightest GRBs (3.7% of lost counts for a count rate of 105 counts.s- 1 over the detection plane in the energy range 4-150 keV) and our model can nicely correct the parts of the lightcurves which are the most affected by dead time effects for very bright GRBs