Visualization of Latent Fingerprint Corrosion of Brass

Abstract:  Visualization of latent fingerprint deposits on metals by enhancing the fingerprint-induced corrosion is now an established technique. However, the corrosion mechanism itself is less well understood. Here, we describe the apparatus constructed to measure the spatial variation (Δ V ) in applied potential ( V ) over the surface of brass disks corroded by latent fingerprint deposits. Measurement of Δ V for potential of 1400 V has enabled visualization of fingerprint ridges and characteristics in terms of this potential difference with Δ V typically of a few volts. This visualization is consistent with the formation of a Schottky barrier at the brass-corrosion product junction. Measurement of the work function of the corroded brass of up to 4.87 ± 0.03 eV supports previous results that suggested that the corrosion product is composed of p-type copper oxides. A model for the galvanic corrosion of brass by ionic salts present in fingerprint deposits is proposed that is consistent with these experimental results.