Study of Corrosion Behavior of Polyuretane/nanoHidroxiapatite Hybrid Coating in Hank Solution at 25 °C

ABSTRACTThe study of corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating in aerated Hank solution at 25 °C by Potentiodinamic and Electrochemical Impedance techniques was realized. The nanohydroxyapatite (nHA) powders were synthesized by ultrasonic assisted co-precipitation wet chemical method and then mixed with pure polyurethane (PU) during the polymerization. Results were supported by SEM morphologic characterization. Results showed that good corrosion resistance of hybrid coating, showing small corrosion product layer formation. Corrosion mechanisms are affected by an increasing of polarization resistance, promoting decreasing in the corrosion rates. Diffusion of ionic species was the governing mechanism in the corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating.

Preliminary Studies Regarding the Behaviour of New Titanium Implants

This paper presents a study concerning a new titanium-based product reached by the specific techniques of powder metallurgy. The product was tested in vitro to corrosion in artificial saliva and in vivo by biological inocuity on sheep and rats for biocompatibility. The chemical composition of artificial saliva solutions used for general corrosion tests were: Fusayama solution; Carter solution; Ericsson solution; Hank solution; Ringer solution. The exposure length was 48, 720, 1440 and 2784 hours. On the sheep, six titanium implants of purity 99.89%, sintered with microporosities and nanoporosities at the surface were administered. Function of implant location, three cm incisions in the skin was made in the following regions: retroscapular for subcutaneous implants, in the tibial diaphysis for the subperiostal implant and in the Latimus Dorsi region for the intramuscular implant. Three different lots of Wistar breed rats were used; the sintered 3.5/1.5 cm titanium implants were placed subcutaneously and intermuscles. Parameters of descriptive statistics were used to assess inflammatory reaction.

Electrochemical Noise Chaotic Analysis of NiCoAg Alloy in Hank Solution

The potential and current oscillations during corrosion of NiCoAg alloy in Hank solution were studied. Detailed nonlinear fractal analyses were used to characterize complex time series clearly showing that the irregularity in these time series corresponds to deterministic chaos rather than to random noise. The chaotic oscillations were characterized by power spectral densities, phase space, and Lyapunov exponents. Electrochemical impedance was also applied the fractal dimensions for the corroded surface was obtained, and a corrosion mechanism was proposed.