Quantitative Evaluation of Pinehole Defects in Corrosion-Resistant Thin Films Prepared by Dry Coating Process

Critical passivation current density(CPCD)method has been applied to the defect evaluation on TiN-coated SUS304 stainless steels.Thin TiN films 0.5-4.0 mum thick were prepared by several kinds of dry coating processes including hollow cathode discharge ion plating，plasma enhanced chemical vapor deposition，dynamic mixing，cathode are discharge ion plating，and activated reactive evaporation。To obtain quantitative relationships between the area fraction of pinhole defects and the thickness of TiN films，the measurement conditions of CPCD were optimized for TiN-coated SUS304 stainless steels.The optimum polarization conditions thus determined are summerized as follows；Solution：deaerated 0.5M-H_2SO_4 0.05M-KSCN at298K，Potential range：-0.45to0.40V(vs.Ag/AgCl，3.33M-KCl)，Scan rate：0.3to0.4m V·s^&lt；-1&gt；.It was found that the area fraction，R_i，of pinhole defects in the TiN films decreased with creasing the thicknms of the TiN_most；the TiN films defects in the TiN films decreased with iness creasing the thicknms of the d&lt；TiN&gt；exceededed2.5mum。The amount of pinehole defects depends also on the preparation method of TiN films.The TiN film4.0mum thick，which was formed by activated reactive evaporation，showed the lowest value of R_i.

Critical passivation current density (CPCD) method has been applied to the defect evaluation on TiN-coated SUS304 stainless steels. Thin TiN films 0.5-4.0mum thick were prepared by several kinds of dry coating processes including hollow cathode discharge ion plating, plasma enhanced chemical vapor deposition, dynamic mixing, cathode are discharge ion plating, and activated reactive evaporation. To obtain quantitative relationships between the area fraction of pinhole defects and the thickness of TiN films, the measurement conditions of CPCD were optimized for TiN-coated SUS304 stainless steels. The optimum polarization conditions thus determined are summerized as follows ;Solution : deaerated 0.5M-H_2SO_4+0.05M-KSCN at 298K,Potential range : -0.45 to 0.40 V (vs. Ag/AgCl, 3.33M-KCl),Scan rate : 0.3 to 0.4 m V・s^<-1>.It was found that the area fraction, R_i, of pinhole defects in the TiN films decreased with increasing the thickness of the films, d_<TiN>, and became almost constant when the value of d_<TiN> exceeded 2.5mum. The amount of pinehole defects depends also on the preparation method of TiN films. The TiN film 4.0mum thick, which was formed by activated reactive evaporation, showed the lowest value of R_i.