Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The Effect of Sodium Chloride Particles on the Atmospheric Corrosion of Pure Copper
KTH, Superseded Departments, Materials Science and Engineering.
KTH, Superseded Departments, Materials Science and Engineering.ORCID iD: 0000-0002-9453-1333
2004 (English)In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 60, no 5, 479-491 p.Article in journal (Refereed) Published
Abstract [en]

The atmospheric corrosion of copper has been investigated after deposition of sodium chloride (NaCl) particles and 10 days of subsequent exposure to clean, humidified air below, near, and above the point of deliquescence of NaCl (at around 75% relative humidity (RH), Microgravimetry, Fourier transform infrared (FTIR) microspectroscopy, scanning electron microscopy with x-ray microanalysis, and scanning Kelvin probe were used to identify corrosion processes and products. The NaCl deposition resulted in the evenly distributed NaCl particle clusters with a diameter of approximately 100 μm. The clusters consisted of individual NaCl particles of <10 μm. The mass gain increased linearly with the amount of NaCl particles added in the range of this study (up to 4 μg/cm2). Even at very low RH (55%), which lies far below the point of deliquescence (75%), copper with NaCl particles added suffered from significant corrosion attack and the mass gain of copper with 4 μg/cm2 NaCl added was about 7 μg/cm2 after 10 days of exposure. At 55% RH, the NaCl particles did not dissolve. However, significant chloride-induced corrosion effects were observed after 10 days, both in the original particle cluster and in a 20-μm-wide outer zone into which chloride ions had dffused radially. At 75% RH, the NaCl particles dissolved and chloride ions diffused to cover the whole surface. Chloride-accelerated corrosion effects resulted in the formation of cuprite (Cu2O) and copper carbonate, mainly in the area of the original particle cluster. The corrosion effects accelerated further at 95% PH, resulting in the formation of Cu2O over the whole surface and copper carbonate in a concentric zone outside the original particle cluster. The distribution of the corrosion products was related to the localization of the anodic and cathodic reactions during the corrosion process.

Place, publisher, year, edition, pages
2004. Vol. 60, no 5, 479-491 p.
Keyword [en]
Atmospheric corrosion, Copper, Deliquescence, Humidity, Sodium chloride particles
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-6892DOI: 10.5006/1.3299244ISI: 000221375100008Scopus ID: 2-s2.0-2542485674OAI: oai:DiVA.org:kth-6892DiVA: diva2:11733
Note

QC 20100909

Available from: 2005-09-27 Created: 2005-09-27 Last updated: 2014-12-11Bibliographically approved
In thesis
1. The role of particles on initial atmospheric corrosion of copper and zinc: lateral distribution, secondary spreading and CO2-/SO2-influence
Open this publication in new window or tab >>The role of particles on initial atmospheric corrosion of copper and zinc: lateral distribution, secondary spreading and CO2-/SO2-influence
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The role of sodium chloride (NaCl) particles and ammonium sulfate ((NH4)2SO4) particles on the initial atmospheric corrosion of copper and zinc was investigated under in situ and ex situ conditions using microgravimetry, FTIR spectroscopy, ion chromatography, scanning electron microscopy with x-ray microanalysis and the scanning Kelvin probe. For the first time, in situ infrared spectra were collected on a micron level during particle induced atmospheric corrosion using a recently developed experimental set-up for in situ FTIR microspectroscopy. Lateral distribution of corrosion and reaction products on copper and zinc surfaces was determined and could be connected with the mechanisms of the initial particle induced corrosion. The recently discovered secondary spreading effect from NaCl electrolyte droplets on metal surfaces was studied under in situ conditions and the effect of CO2 on the spreading process was elaborated. The ambient level of CO2 (350 ppm, 1 ppm = 10-6 volume parts) results in a relatively low secondary spreading effect, whereas the lower level of CO2 (<5 ppm) causes a much faster secondary spreading effect over a large area. At low CO2 concentration alkaline conditions will prevail in the cathodic area, leading to large changes in the surface tension at the oxide/electrolyte interface in the peripherical parts of the droplet. This induces a surface tension driven convective flow of electrolyte from the NaCl droplet. The continuous growth of the secondary spreading area at low CO2 concentration is possible due to the galvanic coupling with the droplet leading to transport of sodium ions to this region and maintenance of the alkaline conditions. At 350 ppm CO2, carbonate formation in the secondary spreading area results in lowering of the pH, increasing the surface tension of the oxide/electrolyte interface and inhibiting the secondary spreading. CO2 strongly affects the NaCl-induced atmospheric corrosion rate of copper. The overall influence of CO2 and NaCl depends on at least three identified mechanisms. At low NaCl particle density, CO2 affects the secondary spreading effect from the electrolyte droplet. This leads to a larger effective cathodic area at low CO2 concentration and a higher corrosion rate. The more alkaline surface electrolyte present at low CO2 concentration also affects the formation of corrosion products and the amount of soluble copper chloride. Whereas the presence of larger amounts of soluble chloride tends to increase the corrosion rate, the formation of CuO results in a more protective surface film which decreases the corrosion rate. This effect was observed at higher NaCl particle densities, where the secondary spreading areas overlapped with adjacent NaCl particle clusters. The formation of CuO leads to lower corrosion rates compared to ambient CO2 concentration in which this phase was not formed. For zinc, the formation of a more protective corrosion product layer was not observed and the corrosion rate is generally higher for low than for ambient CO2 concentration. The presence of NaCl particles on the metal surfaces strongly affects the SO2 interaction with the metal surfaces. The oxidation of S(IV) turned out to be fast at the area of the NaCl-containing electrolyte droplet, both for copper and zinc. On copper surfaces, both sulphate (SO4 2-) and dithionate (S2O6 2-) ions formed which is consistent with a copper catalysed reaction route for sulfite oxidation including the formation of a Cu(II)–sulfito complex as an important step. For zinc, a surface mediated sulfite oxidation process leads to rapid formation of sulphate in the electrolyte droplet area. The presence of SO2 strongly inhibits the secondary spreading due to the decrease in pH induced by absorption of SO2 in the cathodic areas. The presence of gaseous oxidants, such as NO2 and O3, has previously been considered as an important prerequisite for the oxidation of sulfite on copper. The results obtained here suggest that the formation of local electrochemical cells induced by deposited NaCl particles could be another important route for S(IV)- oxidation to sulfate formation. On copper, SO2 was also found to promote the formation of less soluble copper chlorides, such as paratacamite (Cu2(OH)3Cl) and nantokite (CuCl). The electrolyte droplet was dried after 24 hours of exposure due to the formation of less soluble paratacamite (Cu2(OH)3Cl) and nantokite (CuCl) and led to a decrease in the corrosion rate. Thus, SO2 alone promotes the corrosion rate of copper, whereas in the presence of NaCl particles the corrosion rate of copper may slow down due to the formation of insoluble copper chloride compounds. The lateral distribution of corrosion products after exposure of NaCl contaminated copper and zinc surfaces to humid air with gaseous pollutants is a result of the formation of local electrochemical cells at the particles and concomitant differences in chemical composition and pH. For (NH4)2SO4 deposited copper and zinc surfaces the corrosion effects increase with the amount of pre-deposited particles and with the exposure time. On copper, the size of the particles affects the corrosion rate, smaller particles resulting in a higher corrosion rate than larger particles at equal amount of deposition. The formation of Cu2O was the dominant corrosion product after exposure longer than 10 days. (NH4)2SO4 particles result in enhanced Cu2O formation on copper due to a reaction sequence involving catalysis by NH3. The corrosion of copper by (NH4)2SO4 particles was much larger than that induced by NaCl particles. However, for zinc, the (NH4)2SO4 particles lead to smaller corrosion effects than those of NaCl particles. For both particles, significant corrosion attack was observed at relative humidity (RH) lower than the deliquescence point of the salts.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 48 p.
Keyword
atmospheric corrosion, copper, zinc, NaCl particles, (NH4)2SO4
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-431 (URN)91-7178-155-2 (ISBN)
Public defence
2005-10-07, Sal Q2, Osquldas väg 10, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101001Available from: 2005-09-27 Created: 2005-09-27 Last updated: 2010-10-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Leygraf, Christofer

Search in DiVA

By author/editor
Chen, Zhuo YuanLeygraf, Christofer
By organisation
Materials Science and Engineering
In the same journal
Corrosion
Materials Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 144 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf