used instead of gaseous nitrogen as the reactive gas a hard ceramic titanium nitride film 9 was thus formed on the hard chromium plating layer 2 having a large number of pores 6 as shown in fig6 and a sliding member 11 having a large number of oil retaining pores 10 corresponding to the pores 6 in the hard chromium plating layer 2 on the surface was obtained as the final product a plurality of sliding members thus obtained were subjected to an attrition test using a pin on disc type device the test pieces used in the test comprised a disklike base of casting ferrous alloy bearing thereon a 50 u03bc thick hard chromium plating layer 2 and a 2 u03bc thick titanium nitride film the surface of the hard chromium plating layer 2 was honed the sliding members were provided with oil retaining pores having a diameter of about 100 u03bc and a depth of 10 to 15 u03bc the porosity or the proportion of the opening areas was 10 to 15 and the pores were disposed on each intersection of a mesh the test pieces were divided into first to fifth groups depending on the current density and the electrolyzing time in the electrolytic etching process as follows ______________________________________group no current density electrolyzing time______________________________________no 1 50 a dm sup 2 5 min no 2 100 2 min no 3 250 2 min no 4 500 30.