Low temperature curing polyorganosilazane coatings for copper corrosion protection: effect of precursor concentration and relative humidity (RH)

In this study, polyorganosilazane (PSZ) material was used to develop thin hybrid organic-inorganic coatings on copper as a protective barrier against corrosion. The coatings were deposited on the copper substrate by sol-gel route, using solution formulations of 3-aminopropyltriethoxysilane substituted polymethyl(hydro)/polymethylsilazane. The obtained coating were transparent with the advantage of preserving the original aesthetic appearance of the coated material. The effect the PSZ ratio (10-40% w/w) in the depositing solution and relative humidity (RH) of curing process have been investigated. The coating structure was evaluated in function of the curing time by Fourier transform infrared (FTIR) spectroscopy and its morphology by scanning electron microscopy (SEM). Information about barrier properties of the coated samples were obtained by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt% NaCl solution. It was demonstrated that a PSZ coating thickness of about 2 mu m cured at 25 degrees C and 80% RH ensures an enhanced protection for the copper substrate for relatively long time (28 days continuous immersion test).[GRAPHICS].