Papers by Keyword: Crack Free Coating

Abstract: HVOF-sprayed coatings (WC–17%Co) and hard chromium coatings corrosion resistances have been compared through electrochemical polarization test in 3.5% NaCl solution. WC–17%Co alloy coatings were deposited on mild steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. The layers of standard and crack free hard chromium coatings were prepared by using Direct Current (DC) and Pulse Current (PC) electroplating process on the mild steel substrates. Hard chromium coatings was characterized as a reference material, to verify whether HVOF-sprayed coatings are suitable as a hard chromium coatings replacement. The microstructure of the coatings was examined by OM, SEM and XRD. Standard hard chromium coatings passivate in NaCl environment, but crack free hard chromium coatings were prepared by using Pulse Current (PC) electroplating do not passivate. The lowest corrosion current densities (Icorr) were recorded for crack free hard chromium coatings. Comparative electrochemical test results showed that, the Standard hard chromium coating has the highest Icorr and were significantly damaged after the electrochemical tests. It is seem to be that WC–17%Co alloy coatings can be substituted for standard hard chromium coatings but crack free chromium coatings bring new challenge for HVOF-sprayed coatings!

Abstract: Silica coatings were fabricated on stainless steel substrates by electrophoretic deposition (EPD) of aqueous slurries. An cationic surfactant, polyethylenimine (PEI) was used for obtaining positively charged silica particles and coatings on the cathode in order to prevent the anode elution. In addition, in order to prevent formation of cracks in coatings on metal substrates after drying, polyvinyl alcohol (PVA) was added in slurries as a binder. Furthermore, we could obtain crack free coatings after drying by aqueous EPD assisted by sweeping flow.