PURPOSE: To obtain the heat transmission surface with a large number of cavities of aimed shape by alternately executing etching and corrosion-resisting plating repeatedly to spherical graphite cast iron.
CONSTITUTION: When etching spherical graphite cast iron, a section in the vicinity of the surface of cast iron is changed into a porous body consisting of the hemispherical cavities. When a sample surface just after etching is electroplated thinly with a metal having excellent corrosion resistance such as chromium and the porous body is etched again, the cavities, in which graphite particles remain, and the cavities of small opening-section diameters are corroded selectively because of incomplete internal plating though the flat section of the surface with a sufficient corrosion-resisting plating layer is hardly corroded, remaining graphite particles fall in an etching fluid, and the internal diameters of the cavities of the small opening-section diameters increase.
ABE TOSHIHIKO
YONETANI MICHIO
| JPS56127791A | 1981-10-06 |