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Arc-sprayed zinc coatings are more frequently used as anode for the cathodic protection of reinforced concrete structures. However, as with any other conductive coating, zinc should be applied with the highest possible adhesion in order to serve as a durable anode. Factors affecting the adhesion of zinc on concrete are discussed here for the first time. Preheating the concrete surface prior to zinc application has been found to be particularly beneficial. The measured adhesion values have also been found to vary significantly with the pull out procedure.

Electrotribological applications require materials with both high electrical conductivity and wear resistance. For this purpose, it was proposed to develop a copper-based plasma-sprayed coating containing titanium diboride particles. The process for fabricating this Cu-TiB ₂ coating consists of plasma-spraying reactive powders which contain a Cu-Ti alloy and boron. The reaction between the copper alloy and boron proceeds in different steps going from solid-state diffusion of Ti and Cu to the synthesis of TiB ₂in a liquid below 1083 ° C. Plasma-sprayed copper coatings contain finer TiB ₂ crystals than Cu-TiB ₂ materials synthesized in a furnace at 1200 °C. Coatings with vol. 25% TiB₂ have a hardness which is comparable to Cu-Co-Be and Cu-Ni-Be alloys and to Cu-W and Cu-Mo alloys used in spot welding. Their low electrical resistivity of 52 μΩcm could be increased by lowering the oxygen content within coatings and controlling the formation of TiB₂ clusters, the titanium content in solution in copper remaining low after the synthesis reaction., Proceedings NTSC '93, Surface and Coating Technology

A process has been developed for producng cermet coatings containing a ceramic phase finely and well dispersed in a metallic matrix. The method consists of synthesizing and depositing TiB₂-Fe materials by using the arc plasma jet. The thick boride-based coatings obtained by this one-step process have a good abrasive wear resistance., 7th International Symposium on Plasma Chemistry, July 1-5, 1985, Eindhoven, The Netherlands

WO₃ coatings (40±20 μm thick) were deposited onto titanium and tungsten substrates. Scanning electron microscopy and X-ray diffraction were used to characterize WO₃ particles and coatings. The oxygen deficiency of the coatings was determined by thermogravimetry. Depending on the spraying parameters used, WO₂.₉₉ (yellow) and WO₂.₉₇ (dark blue) coatings are obtained. The dark blue coatings are composed of amorphous and unidentified crystalline phases while the yellow coatings contain monoclinic and triclinic phases., 15th International Conference on Metallurgical Coatings, April 11-15, 1988, San Diego, California, USA

The light element direction capabilities of both EELS and windowless (WL) EDX are known (Zaluzec et al 1984). The main advantage of EELS is the absence of overlap which is observed in WL-EDX when more than one low Z elements are present. We have used EELS to study the carbon depletion of TiC caused by the plasma spraying process. A spatial resolution was needed since the structure of these coatings is not homogeneous.

TiB₂‐based materials werr produced by the reaction of ferrotitanium and boron powders. The formation of TiB₂ was studied by differential thermal analysis and X‐ray diffraction. It was observed that TiB₂ is formed at a relatively low temperature through an exothermic reaction. The microstructural characteristics of reaction products are discussed with respect to the reaction temperatures and starting materials. The TiB₂‐based powders were hotisostatically pressed and the density and microhardness of dense specimens were evaluated., 8th Annual Conference on Composites and Advanced Ceramic Materials, January 15-18, 1984, Cocoa Beach, Florida, Series: Ceramic Engineering and Science Proceedings

TiO₂ photoanodes have been prepared by the plasma spray technique on titanium, graphite, and alumina substrates. 25–30 μm thickcoatings display a good adhesion to the substrate and a highly textured surface. Dark and photoelectrochemical propertiesof the photoanodes have been measured in oxygen‐saturated solutions of NaOH at pH 13. It is shown that the performances of the electrodes are quite insensitive to the plasma power or to the TiO₂ powder granulation but are very sensitive to the purity of the spraying material, to the substrate, and also to a heat‐treatment(H₂ or Ar at 800°C followed by a rapid quenching in air). The maximum quantum yield is obtained at 300 nm for heat‐treated TiO₂ . It is about 40% on alumina and 70% on the titanium. The heat‐treatment affects the conductivity, σ, and the surface densityof hydroxyl groups, Noh , of the coatings. For heat‐treated TiO₂ , typical values are σ = 2.4(Ω cm)⁻¹ and Noh = 2.8 x 10¹⁶ cm⁻² . For untreated TiO₂ , typical values are σ = 30.6(Ωcm)⁻¹ and Noh + 2.1 X 10¹⁶ cm ⁻². The J‐V curves of heat‐treated TiO₂ sprayed on alumina extend anodically up to 9.5V (vs. SCE), where film breakdown occurs. For the same film sprayed on titanium and graphite, the anodic dark behavior is similarto that observed for the bare substrates. It is concluded that polycrystalline TiO₂ coatings, produced by the plasma spray technique, can display photoelectrochemical and dark characteristics similar to theones obtained with single‐crystal material.

A limiting feature of the plasma spray process is the need for the powder to melt during its passage through the plasma flame. It is quite impossible to obtain coatings with materials that are difficult to melt. However, metal borides, particularly titanium boride, are attractive. Because of their high melting point, satisfactory coatings based on these materials have not been achieved. To overcome this problem, a process for making TiB₂-Fe coatings was studied. The TiB₂-based coatings were produced by the reaction of ferrotitanium with boron. The TiB₂ formation was first studied by thermal differential analysis and X-ray diffraction. It was observed that TiB₂ is formed at low temperature by an exothermic reaction. The characteristics of the reaction products obtained at different reaction temperatures are described. Agglomeration techniques were used to prepare the reagents: fine powders of ferrotitanium alloy and boron. TiB₂-Fe coatings were produced by plasma spraying the agglomerated powders. The influence of the plasma spray process parameters and the powder preparation techniques on the coating microstructure is discussed. Thick hard coatings comprising compounds of the reagent materials are produced during spraying by this synergetic process. Such coatings may be suitable for wear resistance applications.

Plasma‐sprayed undoped and Si, In or Mg doped α‐Fe2O3 coatings have been characterized by optical microscopy, SEM, SIMS, neutron activation analysis, XRD, and electrochemical measurements.

88th Annual General Meeting of CIM, May 11-15, 1986, Montréal, Quebec

Print copy held at NRC. Digital version available upon request. Contact NRC.NSL-BSN.CNRC@nrc-cnrc.gc.ca, Copie papier conservée au CNRC. Version numérique disponible sur demande. Contactez NRC.NSL-BSN.CNRC@nrc-cnrc.gc.ca

The publication is stored in the NRC Archives., 10th International Thermal Spraying Conference, ITSC'83, May 2-6, 1983, Essen, Germany

La publication est conservée dans les Archives du CNRC.