Electrochemical stripping of hard ceramic chromium nitride coatings A.B. Cristo ´bal a , A. Conde a , J. Housden b , T.J. Tate c , R. Rodrı ´guez d , F. Montala e , J. de Damborenea a, * a Departamento de Corrosio ´n y Proteccio ´n, Centro Nacional de Investigaciones Metalu ´rgicas CENIM-CSIC. Av. Gregorio del Amo 8, E-28040 Madrid, Spain b Tecvac Ltd., Buckingway Business Park, Swavesey, Cambridge CB4 5UG, UK c IC Consultants Ltd, Exhibition road London SW7 2QA, UK d Asociacio ´n de la Industria Navarra, San Cosme y San Damia ´n s/n, E-31191 Pamplona, Spain e Tratamientos Te ´rmicos Carreras, C/ Dr. Almera 85, E-08205 Sabadell, Spain Received 1 June 2004; accepted in revised form 8 March 2005 Available online 21 April 2005 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. D 2005 Elsevier B.V. All rights reserved. PACS: 89.02; 81.65.K; 82.80.F Keywords: Coatings; Chromium; Nitrides; Physical vapour deposition 1. Introduction Physical vapour deposition (PVD) has aroused great interest in recent years since it allows deposition of denser and more compact coatings than are obtained by chemical vapour deposition (CVD), leading to improved chemical and mechanical properties [1]. The technique may be used for a wide range of coatings and hard nitrides or carbides are widely used in the manufacture of tools and forming moulds because of their high wear resistance and low chemical inertia [2]. Of these, TiN coatings are the best established at industrial level. However, CrN coatings have emerged as an alternative in machining applications thanks to thermal stability, low deposition temperature, excellent wear resistance – not only abrasive but also adhesive – and good corrosion resistance [3–10]. This combination of properties makes CrN coatings especially attractive in applications where tools are routinely sub- jected to high temperatures and aggressive atmospheres, e.g. in the plastic injection industry, where the use of these coatings can substantially prolong the service life of coated parts [11]. However, when high cost tools of this type need to be repaired, e.g. when cutting edges need to be sharpened, it is often necessary to remove any coatings and subsequently recoat the repaired surfaces. Similarly, when faults in these coatings are detected it is necessary to remove them in order to redeposit a new defect-free coating. 0040-6090/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2005.03.006 * Corresponding author. E-mail address: jdambo@cenim.csic.es (J. de Damborenea). Thin Solid Films 484 (2005) 238 – 244 www.elsevier.com/locate/tsf