Ternary Ni-W-P films were produced by electroless deposition using baths with different tungsten concentrations. After deposition, the coated surfaces were annealed at 400°C for 1h. Surface morphology and film composition in the as-plated condition were assessed by SEM and EDS analyses, respectively. The crystalline phases after annealing were investigated by X-ray diffraction (XRD). Nanoindentation tests were performed to assess the mechanical properties of the deposited films. Surface roughness was determined by confocal laser scanning microscopy (CLSM). Friction coefficient was evaluated by reciprocating were tests in a nanotribometer. The corrosion behavior was evaluated by potentiodynamic polarization curves. The results showed that the surface morphology, crystallization behavior and corrosion resistance were affected by the tungsten content in the film. The best corrosion performance was obtained for the ternary films after annealing. Hardness, surface roughness and friction coefficient were dependent of the tungsten concentration in the film.

This study reports the high temperature erosion-oxidation (E-O) behavior of conventional and nanostructured Cr3C2-25(Ni-20Cr) coatings prepared by high velocity oxygen fuel (HVOF) spraying. As-received and nanostructured Cr3C2-25(Ni-20Cr) powders with mean crystallite sizes of 145 nm and 50 nm respectively, were used to prepare 120 - 200 µm thick coatings on AISI 310 samples. The E-O behavior of the coatings prepared with the as-received (AR) and nanostructured (NS) powders was determined as weight change in a custom designed rig at room temperature, 450, 700 and 800 ºC. The Vickers microhardness, Young's Modulus and fracture toughness of the AR and NS coatings were determined, and the NS coatings exhibited higher values compared with the AR coatings. The E-O resistance of the NS coating was higher than that of AR coating at all temperatures, and particularly at 800 ºC. The increase in E-O resistance of the NS coatings is due to its superior mechanical properties as well as to the presence of some heterogeneities in the AR coatings. The E-O mechanisms of both types of the coatings are discussed, with special attention to that at high temperatures. The results suggest that at 800 ºC the E-O process is controlled by erosion of the oxide.

Long term isothermal and cyclic oxidation behavior of yttrium dioxide (Y2O3) coated Fe-20Cr alloy was studied. Oxidation tests were carried out in air for periods of up to 200 hours at 1000°C and the oxidation behavior of the alloy was evaluated gravimetrically. The Y2O3 coating reduced markedly the mass gain of the alloy. Energy dispersive spectroscopic analysis of scale sections on oxidized Y2O3 coated specimens revealed a Cr rich layer close to the metal/oxide interface and the presence of Y and Cr near the oxide/air interface, indicating diffusion of Cr through the Y2O3 layer. Further evidence of this diffusion was seen as change in colour of the Y2O3 coating from white to green after prolonged oxidation. X-ray diffraction analysis of the scale revealed perovskite-type YCrO3.This study attributes the increased oxidation resistance of the Y2O3 coated Fe-20Cr alloy to increased oxygen ion diffusion through the Cr2O3 scale due to YCrO3 formation and grain boundary segregated Y ion blocking alloy cation diffusion.

Pitting corrosion of the aluminium cladding of spent nuclear fuels stored in light water pools has been observed. To prevent this, coating of the Al cladding with hydrotalcite (HTC) was proposed. This paper presents the effect of chemical bath and processing parameters on microstructure and corrosion behavior of HTC coatings on alloy AA 6061 specimens. The HTC coating from the high temperature nitrate bath was homogeneous, thicker and consisted of well-defined intersecting platelets than that formed from the room temperature carbonate bath. Electrochemical polarization tests carried out with HTC coated AA 6061 specimens in 0.01 M NaCl revealed that specimens coated with HTC from the nitrate bath and further treated in a cerium salt solution were the most resistant to corrosion. Field tests in which un-coated and coated AA 6061 alloy coupons as well as full-size plates were exposed to the IEA-R1 reactor's spent fuel basin for duration of up to 14 months further corroborated the high corrosion resistance imparted by the high temperature HTC + Ce coating. The mechanism by which the HTC coating and cerium protect the Al alloy is discussed.

A variety of metallic components rely on properties that are specific to the alloy and its surface. Coatings have been extensively used to protect metallic surfaces from the aggressive effects of the environment to which it is exposed. In this investigation, the high temperature oxidation behavior of a FeCr and a FeCrY alloy coated with an aluminium based paint has been studied. The objective was to form the more resistant alumina surface layer on an aluminium free alloy. Aluminium based paint coated and uncoated specimens of the two alloys were oxidized for up to 200 hours at 1000 °C in air. The oxidized specimens were examined in a scanning electron microscope coupled to an energy dispersive system and the surfaces were analyzed by X ray diffraction analysis. The aluminium based paint coating increased the oxidation resistance of the alloys, mainly over extended periods. The FeCrY alloy coated with the Al based paint exhibited the highest oxidation resistance.

The high temperature oxidation and erosion-oxidation (E-O) behavior of steels AISI 1020, 304, 310, and 410 were determined. These steels were selected to evaluate the effect of chromium content on its E-O resistance. The oxidation behavior was determined in a thermogravimetric analyzer. A test rig in which a specimen assembly was rotated through a fluidized bed of erodent particles was used to determine the E-O behavior. Alumina powder (200 µm) was used as the erodent. The E-O tests were carried out in the temperature range 25-600 °C, with average particle impact velocities of 3.5 and 15 ms-1 and impact angle of 90°. The oxidation resistance of the steels increased with chromium content. The E-O behavior of the steels was determined as wastage. The E-O wastage of the steels exposed to particle impact at low velocity was low but increased with temperature above 300 °C. The E-O wastage of the different steels exposed to particle impact at high velocity was quite similar. The wastage increased with increase in temperature above 500 °C. The increases in E-O wastage of the steels observed at temperatures above 300, 400 or 500 °C, depending on the steel, were due mainly to a transition in the dominant wastage process, from 'erosion' to 'erosion-oxidation'.

PtRu/Carbon hybrids were prepared by hydrothermal carbonization process using glucose or starch as carbon sources and reducing agents and platinum and ruthenium salts as catalysts of carbonization process and metals source. The obtained PtRu/Carbon materials were characterized by SEM/EDX, TGA, XRD and cyclic voltammetry. The electro-oxidation of methanol was studied by cyclic voltammetry using the thin porous coating technique aiming fuel cell application. The catalytic activity was dependent of carbon source and time used in the synthesis.

An apparatus to conduct high temperature erosion-oxidation studies up to 850 °C and with particle impact velocities up to 15 m.s-1 was designed and constructed in the Corrosion Laboratories of IPEN. The erosion-oxidation behavior of high velocity oxy fuel (HVOF) sprayed alloy and cermet coatings of Ni20Cr, WC 20Cr7Ni and Cr3C2 Ni20Cr on a steel substrate has been studied. Details of this apparatus and the erosion-oxidation behavior of these coatings are presented and discussed. The erosion-oxidation behavior of HVOF coated Cr3C2 25(Ni20Cr) was better than that of WC 20Cr7Ni, and the erosion-oxidation regimes have been identified for these coatings at particle impact velocity of 3.5 m.s-1, impact angle of 90° and temperatures in the range 500 to 850 °C.