Characterisation of corrosion products in Cr implanted Mg surfaces

In this work we used medium and high fluence Cr implantation, 5 X 10¹⁶ and 5 X 10¹⁷/cm² in an attempt to promote the formation of a Mg-Cr surface system with enhanced corrosion resistance, in particular under neutral and acid conditions. It is also the aim of this work to contribute to the study of the influence and role of the implanted ions in the corrosion progress and mechanisms. Unimplanted and Cr implanted magnesium surfaces were submitted to accelerated corrosion tests by the immersion technique. Concentration depth profiles of the implanted ions were obtained by use of Rutherford backscattering spectrometry (RBS). Information about the H and O contents and depth profiles were obtained by, respectively, elastic recoil detection and RBS, before and after immersion of the unimplanted surfaces in a 3 wt.% NaCl solution saturated with Mg(OH)₂, for different periods of time. The elemental composition and surface distribution of the corroded surfaces were characterised by RBS and proton induced X-ray emission maps obtained with an ion microprobe, and complemented with electron microprobe analysis. Morphology of the affected surfaces was accessed by scanning electron microscopy.