Evaluation of the electrolytic etching depth of a nickel-chromium base alloy used in resin-bonded cast restorations.

This study examined the relation of the electrolytic etching depth of a nickel-chromium base alloy to the etching time. Cast samples (22 mm long, 4 mm wide, 1.5 mm thick) were etched in the Eltrokor etching unit, using Korolyt A as the etching solution with a constant current density of 400 mA/cm2. On each sample an approximately 3 mm long area was etched for 5, 7, 9, and 11 minutes. Between each etched area, a field of approximately 2 mm long remained unetched. The surface of each sample was scanned with a profilometer. The distance of the compensation plane of the scanned etched profile to the unetched areas was then measured for each etching time. The average etched depth with an etching time of 5 minutes is 30.4 microns (SD 2.39); with a time of 7 minutes the depth is 44 microns (SD 3.49); with a time of 9 minutes the depth is 59.8 microns (SD 4.10); and with an etching time of 11 minutes the depth is 72.9 microns (SD 2.94). Taking the average of all etching depths per etching time, the average loss of substance is 6.409 microns per minute etching time.