PLASMA-POLYMERIZED COATINGS OF TRIMETHYLSILANE DEPOSITED ON COLD-ROLLED STEEL SUBSTRATES .2. EFFECT OF DEPOSITION CONDITIONS ON CORROSION PERFORMANCE

Trimethyl silane (TMS) plasma-polymerized films were deposited on cold -rolled steel (CRS) under different conditions. The films were charact erized by angular-dependent Xray photoelectron spectroscopy (XPS), Aug er electron spectroscopy (AES) and time-of-flight secondary ion mass s pectrometry (TOFSIMS). The complementary information generated by thes e surface techniques gave detailed information on the film composition . The corrosion performance of the plasma films was estimated by elect rochemical impedance spectroscopy (EIS) and by exposure in a humidity test. All films were Si-based and their composition was a function of the deposition conditions and the plasma cleaning of substrate prior t o deposition. A reducing plasma for metal surface treatment resulted i n a film with the highest impedance. The plasma film surfaces were hig hly oxidized. The contact angle was the lowest for plasma films deposi ted from a mixture of TMS and oxygen and their corrosion performance w as the poorest.