Contamination of Electronic Equipment after an Extended Urban Exposure

Abstract

Water soluble contaminants on electromechanical telephone switching equipment exposed for up to 40 years to the New York City environment have been chemically analyzed by a combination of methods, and their moisture pickup characteristics have been monitored by instrumental gravimetric techniques. Samples were collected from structural surfaces by extraction with filter paper squares moistened with distilled water. Elements with atomic numbers greater than 11 were identified by energy dispersive x‐ray analysis. Selected anions were identified by microchemical tests and infrared spectroscopy. Nitrate and sulfate concentrations of 46 samples from one location were measured using nitrate and lead ion selective electrodes (the latter for titration of sulfate). Several hundred samples from this and four other locations were analyzed using a chloride ion selective electrode. On zinc surfaces, chloride concentrations averaged 27 μg/cm2 for typical locations, while sulfate and nitrate concentrations averaged 48 and 6 μg/cm2, respectively. On aluminum surfaces, chloride concentrations averaged <2 μg/cm2, while sulfate and nitrate concentrations averaged 25 and 3 μg/cm2, respectively. Moisture pickup by contaminants on zinc and aluminum surfaces was found to occur above 26 and 46% RH, respectively.