Initial Atmospheric Corrosion of Zinc Exposed to Formic Acid, Investigated by in Situ Vibrational Sum Frequency Spectroscopy and Density Functional Theory Calculations

Abstract

Vibrational sum frequency spectroscopy (VSFS) and ab initio density functional theory (DFT) calculations of formic acid on ZnO/Zn have been performed in order to understand the first step of atmospheric corrosion on zinc initiated by formic acid. In addition, infrared reflection absorption spectroscopy (IRAS) has been employed to complement the surface sensitive VSFS results to identify the corrosion products. Oxidized polycrystalline zinc samples were exposed to 120 ppb formic acid in either humid or dry air where, the formic acid adsorption on ZnO/Zn is observed to have a low dependence on the humidity, as deduced by VSFS. Formate is formed on the surface in both dry and humid air and stabilized in configuration after about 90 min exposure in 120 ppb formic acid as seen in the VSFS results. This is evidenced by the occurrence of the CH and symmetric COOvibrations of the formate ion. The DFT calculations support the VSFS results, showing a coordination of the formate to zinc ions without participation from water molecules. † Part of the special section "Physical Chemistry of Environmental Interfaces".

Alkanethiols as Inhibitors for the Atmospheric Corrosion of Copper Induced by Formic Acid: Effect of Chain Length

“…A detailed description of the VSFS cell is provided elsewhere. 22 Before the in-situ VSFS measurements started the cell was purged with dry nitrogen to remove oxygen and humidity from the cell.…”

“…It should be noted that unlike zinc exposed to humidified air with formic acid, 22 the reaction products (copper formate) on copper under current exposure conditions do not form ordered structures and therefore are not observed in the CH region since VSFS peaks to be observed require a net orientation of the adsorbed species.…”

Octadecanethiol as Corrosion Inhibitor for Zinc and Patterned Zinc-Copper in Humidified Air with Formic Acid

“…Overall, the results suggest that ODT can function as a temporary corrosion inhibitor in representative indoor environments on zinc and zinc with zinc-copper junctions. It is nowadays well established that carboxylic acids, such as formic [1][2][3][4] or acetic acids, 5,6 may cause corrosion of several metals, including copper, nickel and zinc, in a variety of indoor atmospheric environments.7-11 Such acids are generated through out-gassing of organic constituents from, e.g., wood, 12,13 paper, 12,14 and paint, 13 followed by gradual oxidation to carboxylic acids. The corrosion effects they cause may decrease the quality and performance of electronic materials, 15 military equipment, 16 and deteriorate our cultural heritage.…”

“…Overall, the results suggest that ODT can function as a temporary corrosion inhibitor in representative indoor environments on zinc and zinc with zinc-copper junctions. It is nowadays well established that carboxylic acids, such as formic [1][2][3][4] or acetic acids, 5,6 may cause corrosion of several metals, including copper, nickel and zinc, in a variety of indoor atmospheric environments.…”

“…It is nowadays well established that carboxylic acids, such as formic [1][2][3][4] or acetic acids, 5,6 may cause corrosion of several metals, including copper, nickel and zinc, in a variety of indoor atmospheric environments. [7][8][9][10][11] Such acids are generated through out-gassing of organic constituents from, e.g., wood, 12,13 paper, 12,14 and paint, 13 followed by gradual oxidation to carboxylic acids.…”