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

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Self-assembled mono-and multilayers of stearic acid have been examined as corrosion protection systems for copper-nickel alloy in 3% sodium chloride solution. We found that self-assembled multilayers of stearic acid provide more efficient and durable corrosion protection to copper-nickel alloy than just a single monolayer. Electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy, were used to determine the protective properties of the stearic acids films. Sum frequency generation spectroscopy, atomic force microscopy, contact angle measurements and ellipsometry were used to evaluate structural properties and thickness of the surface layers. It was found that the increase of corrosion protection from mono-to multilayer films depends on the number of layers that are formed but also on their homogeneity.

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confidence: 99%

The Influence of Thickness of Stearic Acid Self-Assembled Film on Its Protective Properties

Gretić

Mioč

Čadež

et al. 2016

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“…Another reason is that the penetration of the corrosion stimulators, water (H 2 O), formic acid (HCOOH) and oxygen gas (O 2 ) in our case, through the self-assembled monolayer occurs slower for longer alkyl chain lengths. 19 However, even for ODT, the corrosion protection gradually decreases with increasing exposure time, and over a similar time scale the conformational order in the adsorbed ODT layer decreases. 24 A major aim of this study is to explore the potential of ODT as a corrosion inhibitor on zinc and on Zn-Cu patterned samples.…”

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confidence: 99%

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confidence: 99%

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

Forslund

Leygraf

Claesson

et al. 2014

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The corrosion inhibition efficiency of octadecanethiol (ODT) for zinc and a zinc-copper patterned model sample (Zn-Cu) has been explored during exposure in an atmosphere that mimics indoor atmospheric corrosion containing humidified air (80% relative humidity at 20 • C) and formic acid (around 100 ppb). The corrosion kinetics were monitored in situ with infrared reflection absorption spectroscopy, and the local nature of corrosion effects post-analyzed with complementary scanning electron microscopy, atomic force microscopy and confocal Raman spectroscopy. ODT shows initially a corrosion inhibiting ability both on zinc and on Zn-Cu. This ability decreases with time due to local removal of ODT, which causes micro-galvanic effects that eventually result in corrosion rates that exceed those for the uncovered samples. On bare and ODT-covered samples, the presence of a copper-zinc junction results in both accelerated corrosion and in structurally more developed corrosion products. 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.13 A common situation is the simultaneous exposure of two metals in electrical contact. The galvanic corrosion that follows leads to an accelerated corrosion of the less noble metal. Both zinc and copper are important engineering materials widely used in everyday life. Brass is a copper-zinc alloy that has improved machinability compared to unalloyed copper. The corrosion of brass is more complex than unalloyed copper due to possible galvanic effects that favor selective zinc dissolution, which leads to dealloying of a copper-rich matrix.17 Micro-galvanic effects are established between local anodes and local cathodes on the surface, whereby the galvanic corrosion kinetics are dependent on the electrochemical potential difference and the area ratio between the anode and cathode. 18 In order to explore the mechanism of micro-galvanic corrosion effects, well-defined Zn-Cu patterned samples were studied previously during exposure to humidified air with addition of formic acid. 18 It was found that the micro-galvanic effects observed on the patterned sample not only resulted in accelerated corrosion kinetics but also in structurally more developed corrosion products with characteristic hemispherical features not seen on pure zinc or copper metals.In this paper we present data on micro-galvanic effects on the Zn-Cu patterned ...

“…It is a challenge to follow the formation of extremely thin corrosion layers (a few monolayers to ∼1 nm) on copper surfaces in real-time in ambient environments even using current state of the art characterization techniques, and new sensitive methods are desirable. Many studies have focused on rather aggressive environments such as (air-saturated) salt solutions, 9,11,12,15 air with high humidity and traces of other oxidants, 3,13,19 or elevated temperature (>150 • C) 14 where signals are relatively high and easier to measure. Few studies are available for mildly corrosive ambient environments: Laibinis et al 7 studied the oxidation of Cu protected by various nalkylthiols at ∼20 • C and <30% relative humidity (RH) using X-ray photoelectron spectroscopy (XPS), Jennings et al 8 at ∼20 • C and ∼10% and 100% RH using XPS and contact angle measurements, and Hutt et al 16 at 20-25 • C and ∼50% RH, ∼4 • C and ∼50% RH, as well as −30 • C using XPS.…”

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Nanoplasmonic Sensing for Monitoring the Initial Stages of Atmospheric Corrosion of Cu Nanodisks and Thin Films

Schwind

Hosseinpour

Langhammer

et al. 2013

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Nanoplasmonic sensing as a powerful experimental technique for corrosion kinetics monitoring is demonstrated. Its versatility is illustrated by studies of initial corrosion carried out on model systems consisting of copper nanodisks and extended copper films in both dry (<0.5% relative humidity, RH) and humid (65 ± 5% RH) air. Samples with and without a protective self-assembled monolayer of octadecanethiol (ODT) were studied. Thus, we studied four different corrosion situations. Two versions of the technique were employed, direct and indirect nanoplasmonic sensing (INPS). The former used disk-shaped nanoparticles as both sample structures and sensing particles, the latter used extended films as the sample, with the nanoplasmonic sensing particles embedded under the sample. Corrosion kinetics were recorded with high sensitivity and high temporal resolution (submonolayer detection limit; temporal resolution 1-2 seconds). In dry air, six times lower oxidation rates were observed for ODT-covered Cu compared to bare Cu, demonstrating the protection efficiency of the ODT as a corrosion inhibitor. In humid air, a higher oxidation rate was measured for both bare (2.4 times higher) and ODT-covered (1.7 times higher) samples, compared to the same samples exposed to the dry air environment. Oxidation occurred first after a short induction period during which water was adsorbed. For the Cu nanodisks (direct sensing) and Cu films (indirect sensing) studied here, very similar oxidation kinetics were observed.