Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes the work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in The Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, © American Chemical Society after peer review. To access the final edited and published work see http://dx.doi.org/10.1021/jp201718b A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription.

This Article reports the use of scanning electrochemical microscopy (SECM) for the quantitative study of acid-induced dissolution. An ultramicroelectrode (UME) is used to generate a flux of protons galvanostatically just above a sample surface, creating controlled acid challenges relevant to acid erosion. The electrochemical technique produces etch features in the sample, which are characterized by white light interferometry (WLI). The technique has been applied to bovine enamel where understanding the kinetics of dissolution is important in the context of acid erosion. Dissolution has been observed as a fast process, but the high rates of mass transport in SECM allow the surface kinetics of dissolution to be evaluated. Key attributes of SECM for these studies are the ability to deliver high, controllable, and local acid challenges in a defined way and that multiple dissolution measurements can be performed on one sample, eliminating intersample variability effects. A novel moving boundary finite element model has been designed to describe the etching process, which allows the etch kinetics to be evaluated quantitatively, simply by measuring the size and shape of etch features over time.

(2013) Holistic approach to dissolution kinetics : linking direction-specific microscopic fluxes, local mass transport effects and global macroscopic rates from gypsum etch pit analysis. Physical Chemistry Chemical Physics, Volume 15 (Number 6). pp. 1956pp. -1965pp. . ISSN 1463 Permanent WRAP url: http://wrap.warwick.ac.uk/54301/ Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes the work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement: None A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. Dissolution processes at single crystal surfaces often involve the initial formation and expansion of localized, characteristic (faceted) etch-pits at defects, in an otherwise comparatively unreactive surface. Using natural gypsum single crystal as an example, a simple but powerful morphological analysis of these 10 characteristic etch pit features is proposed that allows important questions concerning dissolution kinetics to be addressed. Significantly, quantitative mass transport associated with reactive microscale interfaces in quiescent solution (well known in the field of electrochemistry at ultramicroelectrodes) allows the relative importance of diffusion compared to surface kinetics to be assessed. Furthermore, because such mass transport rates are high, much faster surface kinetics can be determined than with existing 15 dissolution methods. For the case of gypsum, surface processes are found to dominate the kinetics at early stages of the dissolution process (small etch pits) on the cleaved (010) surface. However, the contribution from mass transport becomes more important with time due to the increased area of the reactive zones and associated decrease in mass transport rate. Significantly, spatial heterogeneities in both surface kinetics and mass transport effects are identified, and the morphology of the characteristic etch features 20 reveal direction-dependent dissolution kinetics that can be quantified. Effective dissolution velocities normal to the main basal (010) face are determined, along with velocities for the movement of [001] and [100] oriented s...