CorrotionScience, Vol. 20, pp. 27 to 39 PergamonPreu Ltd. 1980.Printedin GreatBritain. THE THERMAL OXIDATION OF ION-IMPLANTED ZIRCONIUM* G. G. BENTINI Laboratorio LAMEL-CNR, Bologna, Italy M. BERTI,A. CARNERA,G. DELLA MEA, A. V. DRIGO, S. Lo RUSSOand P. MAZZOLDI Istituto di Fisica, Unive~ita di Padova, Italy Uniti~ G.N.S.M.-C.N.R. and G. DEARNALEY AERE Harwell, Didcot, England Abstract--Tbe thermal oxidation of polycrystaUine zirconium implanted with 21 different ion species has been studied by using the nuclear reaction ~60(d,pOrTO. A very good agreement has been found between the oxidation kinetics of unimplanted zirconium as determined by the nuclear reaction and those previously measured gravimetrically. Oxidation kinetics show a time dependence which is cubic or parabolic depending upon the surface treatment before oxidation. Ion implantation produces significant dmnges in oxidation rate but the time dependence remains the tame. A strong correlation has beta found between the behaviour of ion implanted systems and that reported for binary alloys, confirming the hypothesis that the ionic size of the additive is the major paramete, governing the infl~ upon the oxidation of zirconium. The implanted species which inhibit oxidation poc___~e~__ ionic radii lying betwem 80~o and 100~. of that of Z# +. An explanation of their beneficial effect based on an increase of the plasticity of the growing oxide is presented. INTRODUCTION Tim LOW thermal neutron capture cross section and good corrosion resistance of zirconium and its alloys have led to their widespread use in water-cooled nuclear reactors. There have therefore been many studies 1 of the oxidation of these alloys in oxygen or steam, particularly in the temperature range up to .500°C. It has been established that oxidation proceeds by oxygen transport into the metal, but the role of additives even in low-concentration binary alloys has not been well established. It is by no means simple to prepare a wide variety of alloy specimens with con- trolled composition and similar grain size. Differences between their oxidation behaviour have sometimes been attributed to heat treatment and the extent and morphology of intermetallic formation. ~ A fine and uniform distribution of second phase precipitates in a homogeneous matrix provides the optimum resistance to oxidation. ~ *Manuscript received 19 December 1978; in revised form 2S March 1979. tPaper presented at the Meeting on 'Ion Implantation and Ion Beam Analysis Techniques in Corrosion' held at the University of Manchester Institute of Science and Technology in the Corrosion and Protection Centre, 28-30 June 1978. 27