Electrochemical stripping of hard ceramic chromium nitride coatings

Abstract

Chromium nitride—CrN—coatings have emerged as an alternative in machining applications thanks to thermal stability, low deposition temperature, excellent wear resistance and good corrosion resistance. However, under some circumstances it is often necessary to remove these kinds of coatings without attack of the base metal surface. In this work a stripping method based on electrochemical techniques has been developed to strip chromium nitride coatings in an oxidising alkaline solution process. Under galvanostatic conditions, it has been applied to strip CrN coatings with different configurations—monolayer and multilayer. The greater activity of the nitride in this medium leads to the formation of more soluble species. The complete removal of the chromium nitride layer is indicated by a sudden rise in the potential in time, which allows simple control of the stripping process. The surface appearance of the samples at the end of the coating removal process is good, since pitting is not detected and surface homogeneity is preserved, which are necessary conditions for redeposition of this type of coating.