Elimination of sodium cyanide and vapor degreasing from the passivation process.

摘要

This report is an examination of the vapor degreasing and alkaline descaling steps in the passivation process. Since parts that are to be passivated are fairly clean, the vapor degreasing step may be redundant. Sodium cyanide is a component of the alkaline descaling solution and would be desirable to eliminate because of environmental concerns. Evaluations were performed to determine if the vapor degreasing step could be eliminated and the cyanide removed from the descaling solution. The stainless steels used in these evaluations were 15-5 PH and 303 SE wrought materials and 17-4 PH casting material. Samples of these stainless steels were contaminated with five materials normally encountered prior to the passivation process. The contaminated samples were then passivated with the standard process and the modified process in which the vapor degreasing step was eliminated and the sodium cyanide removed from the descaling solution. After the passivation of these contaminated samples, Auger Electron Spectroscopy (AES) was used to measure the effectiveness of the standard and modified passivation processes.