Effect of Sodium Chloride Particles on the Atmospheric Corrosion of Pure Copper

A laboratory environment chamber with a constant deposition rate of NaCl was built. With this chamber, the corrosion behavior of Cu during constant NaCl deposition was investigated with different CO 2 concentrations and ultraviolet (UV) illumination. XRD and coulometric reduction techniques were used to identify and quantify the corrosion products. An Na 2 CO 3 solution was found to be more suitable than KCl solutions for quantification of Cu corrosion products. Cuprite was always the dominant corrosion product during exposure of Cu in various environments. UV illumination accelerated formation of cuprite significantly but had very little effect on formation of cupric corrosion product. CO 2 in the environment was important in determination of cupric corrosion products. With 350 ppm CO 2 , paratacamite was the dominant product, while tenorite was dominant with <1 ppm CO 2 . This explains why tenorite is not a common cupric corrosion product in the field. Pitting corrosion was always the dominant form of corrosion at the beginning of the exposure period but uniform corrosion dominated at later times. The new environment chamber enables the determination of Cu corrosion kinetics in the lab, especially the formation of paratacamite, which provides insight into Cu atmospheric corrosion in the field. Atmospheric corrosion of Cu in the field and in laboratory chambers has been widely studied because of the use of Cu in electronics and architecture.1-6 NaCl has a strong accelerating influence on Cu corrosion in the field, especially in marine environments. 5,6 The effects of NaCl have also been investigated in laboratory-based atmospheric corrosion studies.7-12 NaCl has been shown to accelerate the breakdown of the naturally formed and protective copper oxide by the formation of copper chloride complexes, 11 especially at high relative humidity (RH). When the RH is higher than the critical relative humidity of NaCl, 75%, 13 deposition of 4 μg /cm 2 of NaCl before exposure increases the Cu corrosion rate of Cu by about one order of magnitude during 10 days exposure. 8 NaCl has also been shown to be critical for formation of Cu 2 (OH) 3 Cl, a common corrosion product found in marine environments. 3 In the presence of NaCl, cuprite (Cu 2 O) can be readily oxidized to atacamite or paratacamite, which are isomers of Cu 2 (OH) 3 Cl.12 However, because of difficulties generating a constant deposition rate of NaCl during lab exposure, there is a lack of information on the kinetics of Cu 2 (OH) 3 Cl formation and how Cu 2 (OH) 3 Cl affects the Cu corrosion rate.Methods used to introduce NaCl onto a surface for laboratory study of atmospheric corrosion of Cu and other metals include deposition of NaCl particles before exposure by fast evaporation of ethanolic NaCl solution, 8,11 thermophoretic deposition 14,15 or printing. 16 A disadvantage of prior deposition for the study of Cu corrosion kinetics is that the available NaCl in the environment decreases with time due to formation of Cu 2 (OH) 3 Cl or CuCl during exposure. Furthe...

mentioning

confidence: 99%

mentioning

confidence: 99%

Atmospheric Corrosion of Cu during Constant Deposition of NaCl

Lin

Frankel

2013

“…[16][17][18][19] In the 1950s, Preston and Sanyal, 16 and, later, Ericsson 17 reported the initiation and sustainment of corrosion under NaCl crystals down to 58% RH (the lowest RH tested) through isohumidity experiments. Since that time, the possibility for initiation of corrosion under crystalline NaCl particles has received little attention, and, of those that have reported this occurrence, ∼50% RH appears to be the minimum.…”

Section: Introductionmentioning

confidence: 99%

Effect of Relative Humidity on Corrosion of Steel under Sea Salt Aerosol Proxies

Schindelholz

Risteen

Kelly

2014

This paper is the first of two that examine the relationship between relative humidity, the hygroscopic behavior of sea salt aerosol proxies, and the atmospheric corrosion of mild steel contaminated with them. Here, the association between the deliquescence phase transitions (solid-aqueous) of a single salt, NaCl, and the corrosion response of steel contaminated with this salt is examined. Specific focus is given to mechanisms that allow corrosion below the deliquescence relative humidity of NaCl (76% RH). Mild steel loaded with aqueous NaCl drops or crystals (9 μg · cm −2 ) was subjected to isohumidity exposures for up to 300 days. The resulting damage was quantified by optical profilometry. The corrosion chemistry that developed was identified using EDS and Raman spectroscopy. The wetting and drying of simulated corrosion chemistries were characterized by impedance measurements across an interdigitated electrode sensor. Taken together, these results show that corrosion can initiate by adsorbed water on NaCl crystals at as low as 33% RH. At 53% RH and above, attack proceeded at rates comparable to that observed above the deliquescence RH due to the development of hygroscopic corrosion chemistry. The governing role of the hygroscopic properties of this chemistry on attack rate and morphology is discussed.

“…In fact, corrosion of copper has been observed at 55% RH in the presence of NaCl particles. 38 The important reaction pathways seem to be 1 and 4, as was the case for the deliquesced surface at 90% RH. However, at 60% RH, the reduction charge is slightly higher with UV, indicating a stronger contribution of pathway 4 than at 90% RH.…”

Section: C154mentioning

confidence: 99%

Effects of Sodium Chloride Particles, Ozone, UV, and Relative Humidity on Atmospheric Corrosion of Silver

Liang

Allen²,

Frankel

et al. 2010

Self Cite

The corrosion of Ag contaminated with NaCl particles in gaseous environments containing humidity and ozone was investigated. In particular, the effects of relative humidity and UV light illumination were quantitatively analyzed using a coulometric reduction technique. The atmospheric corrosion of Ag was greatly accelerated in the presence of ozone and UV light. Unlike bare Ag ͑i.e., with no NaCl particles on the surface͒, Ag with NaCl exhibited fast corrosion even in the dark, with no UV in the presence of ozone. Samples exposed to different outdoor environments and samples exposed in a salt spray chamber were studied for comparison. Ag corroded at extremely low rates in a salt spray chamber partly because of the combined absence of light and oxidizing agents such as ozone. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3310812͔ All rights reserved. Despite their widespread use, the results of accelerated atmospheric corrosion tests such as ASTM B117 often do not correlate well with field exposures.1 As shown below, silver is an example of this phenomenon as silver oxidizes readily during outdoor field exposure but is barely attacked in a salt spray chamber. Clearly, some controlling factors of the chemical and electrochemical reactions in the field exposures are not accurately reproduced in the salt spray chamber environment.Atmospheric corrosion of silver is affected by factors such as relative humidity ͑RH͒, 2-4 airborne pollutants, 5,6 and temperature. Traditional atmospheric corrosion studies of Ag have focused mainly on sulfidation 3,7-9 as silver reacts strongly with sulfurcontaining species. The absence of such species in the ASTM B117 test is one reason why silver is relatively inert in the salt spray environment. However, there has been little focus on the effects of chloride and photoassisted corrosion.In a previous paper, 10 the effects of ozone, UV radiation, and RH on the atmospheric corrosion of bare silver were studied. Atomic oxygen generated by the photolysis of ozone by UV radiation reacted quickly with bare silver to form silver oxide. However, 254 nm UV radiation or ozone alone did not cause any corrosion of Ag within the exposure period. The corrosion rate of bare silver was relatively independent of RH, and it was suggested that the initial chemisorption of atomic oxygen or OH radical under wet conditions is relatively unaffected by RH. The effects of chloride on these reactions are not known. Furthermore, the atmospheric corrosion rate of metals in the field is typically dependent on RH as a result of the interactions of water with salts on the surface. 11Sea-salt aerosols can play a critical role in the atmospheric corrosion process. Cole et al. described marine aerosol formation, chemistry, reaction with atmospheric gases, transport, deposition onto surfaces, and reaction with surface oxides.12 The small size of sea-salt aerosols allows them to be carried away by the wind to places far away from the sea.13 These aerosols are created by physical processes such as the bursting of air...