Magnetron sputtered SiC coatings as corrosion protection barriers for steels

Silicon carbide films between 2.3 and 3.0 mum were deposited on ATSI 304 st ainless steel (SS), carbon steel (CS) and crystalline silicon from a SiC ta rget in a magnetron sputtering system. Good mechanical properties were obta ined for the films by carefully controlling the deposition parameters. Resu lts of scratch tests revealed that adhesion of the films is a function of d eposition parameters and substrate type. Additionally, an influence of subs trate preparation prior to deposition was also observed. Critical loads of 20 N, 8 N and 5 N were obtained in case of Si, SS and CS substrates, respec tively. Vickers micro-hardness values were between 10 and 30 GPa, films on SS being harder than films on CS. The behavior of the fil;ns as corrosion p rotection barriers in aggressive environments was evaluated by immersion te sts and electrochemical impedance spectroscopy measurements. Films on SS ex hibited a better corrosion resistance than those on CS. Their adhesion to t he SS was outstanding, even after a long time of immersion in a HCl 0.8 M s olution, showing that they are efficient protection barriers. The corrosion process of the substrates starts at micro-pores present in the films so th at corrosion pits all over the surface of the samples can be observed. (C) 2000 Elsevier Science B.V. All rights reserved.