Magnetron sputtered Au–Pd–In alloys: microgravimetric and electrochemical characterisation in simulated physiological solutions

Abstract

An electrochemical quartz crystal microbalance (EQCM) has been applied in corrosion sensing of magnetron sputtered Au–Pd–In alloy in simulated physiological solutions. The piezoelectric resonators were prepared by alloy deposition on quartz substrates by a DC magnetron-sputtering (MS) technique. X-ray photoelectron spectroscopy (XPS) analysis showed that the deposit composition was similar to that of the MS target, which was a commercially available casting alloy. X-ray diffraction indicated that the sputtered alloy has a crystalline structure. Measurements by using impedance spectroscopy and DC voltammetry showed some differences in electrochemical behaviour of both sputtered and cast alloy; however, these data did not indicate superior corrosion resistance of the sputtered specimen. Alloy corrosion has been studied by EQCM in three simulated physiological solutions: 0.9 N NaCl, 0.1 N NaCl+0.1 N lactic acid and artificial saliva. The EQCM indicated corrosion as increase in electrode mass, which was due to accumulation of corrosion products on the surface. The mass gain curves were similar in both neutral (pH 6) and acidic (pH 2.2) solutions, what implies dissolution of corrosion products in both media to be insignificant. XPS analysis showed that In 2O 3 was the main corrosion product on the surface. Corrosion current calculations from the mass curves were undertaken, which yielded the same corrosion rate assuming different oxides on the surface. The average corrosion rates in oxygenated 0.9 N NaCl and 0.1 N NaCl+0.1 N lactic acid solutions were similar and about twice as high as that in saliva.