MULTICOMPONENT Al-BRONZE COATINGS THERMALLY SPRAYED ONTO TIN BRONZE SUBSTRATE: MICROSTRUCTURAL, MECHANICAL AND CORROSION CHARACTERIZATION IN A 3.5% NaCl SOLUTION

In this work, multicomponent Al-bronze alloys coated Tin-Bronze substrates, fabricated by thermal flame spraying, are characterized by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. Mechanical characterizations are also presented: microhardness measurement and friction coefficient. The electrochemical behavior of tin-bronze samples uncoated and coated with multicomponent Al-Bronze coatings is studied in NaCl 3.5% solutions using potentiodynamic polarization curves and polarization resistance measurements. The microstructure of the coatings has a lamellar morphology. Each lamella is constituted of a mixture of Cu3Al globular micro precipitates (beta-phase) uniformly distributed over the solid solution matrix (alpha-Cu). An oxide based on Cu, Al and Fe is also present in very low concentration. beta-phase is unexpected because it is present only above 570 degrees C in the Cu-Al phase diagram. Compared with the tin-bronze substrate, multicomponent Al-bronze coatings show a friction coefficient three times lower and have a better electrochemical behavior in 3.5% NaCl solution.