Search

Abstract: The recent restriction in the use of chromium VI gave a new impulse in the field of anti-corrosion treatment for an alternative solution. A promising route seems to be the deposition of a thin ceramic layer on the metallic surface. In this study, four zirconia primers have been deposited on 1050 aluminium sheets by sol–gel process. Sol preparation was obtained starting from two different precursors and two curing temperatures were tested. Surface microstructure and chemical composition were determined by AFM and XPS for all samples. Electrochemical Noise Analysis (ENA) was used in Harrison''s solution to evaluate the corrosion resistant features of the samples. Tests have been also performed on samples protected by polyester topcoat deposited on the aforesaid primers. AFM analysis revealed that, for all the samples, covering and structure of the coating were uniform. XPS depth profiling allowed concluding that film thickness was in the range from 18 to 30 nm and that chemical composition was constant through primer thickness. Corrosion tests demonstrated that zirconia primers showed good performances in terms of corrosion resistance, comparable to chromate and fluotitanate layers industrially prepared. Topcoated samples gave an optimal corrosion resistance. [Copyright &y& Elsevier]

Abstract: Reactive plasma spraying (RPS) technology has been used to produce high thickness (>100μm) films of composite Ti–TiN–Ti x N y coatings. Reactively sprayed coatings obtained from SP700 (Ti–4.5Al–3V–2Mo–2Fe) and Ti6242 (Ti–6Al–2Sn–4Zr–2Mo) powders, deposited onto flat substrates of Ti–6Al–4V, have been investigated. X-ray diffraction (XRD) and micro-hardness measurements have been used to characterize the crystallographic features and differences between the hardness of cross-section and surface. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques have been used to determine the morphology and surface chemical composition of the coatings. Back-scattered electron imaging has revealed the distribution of Ti and TiN in the composite material. Obtained results evidenced a sharp interface between the coating and substrate in terms of the profile of chemical composition. The presence of unmelted Ti particles as well as the formation of nitrides was observed. [Copyright &y& Elsevier]