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Effect of Chloride Ion Concentration on the Galvanic Corrosion of a Phase Brass by Eccrine Sweat

NCJ Number
Journal of Forensic Sciences Volume: 57 Issue: 4 Dated: July 2012 Pages: 1070-1074
Andrew Meekins, M.Chem.; John W. Bond, D.Phil.; Penelope Chaloner, Ph.D.
Date Published
July 2012
5 pages
This study examined the effect of fingerprint sweat on certain metals.
Inductively coupled plasma mass spectrometry measurement of the relative concentration of sodium, chloride, calcium, and potassium ions in eccrine sweat deposits from 40 donors revealed positive correlations between chloride and sodium (p = 0.684, p less than 0.01) and chloride and calcium ions (p = 0.91, p less than 0.01). Correlations between ion concentration and the corrosion of a phase brass by the donated sweat were investigated by visual grading of the degree of corrosion, by measuring the copper/zinc ratio using energy-dispersive X-ray spectroscopy, and from a measurement of the potential difference between corroded and uncorroded brass when a large potential was applied to the uncorroded brass. An increasing copper/zinc ratio (indicative of dezincification) was found to correlate positively to both chloride ion concentration and visual grading of corrosion, while visual grading gave correlations with potential difference measurements that were indicative of the preferential surface oxidation of zinc rather than copper. Abstract published by arrangement with John Wiley & Sons.