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Corrosion-induced release of zinc and copper in marine environments
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This licentiate study was initiated by copper, zinc and galvanized steel producers in Europe, who felt a need to assess runoff rates of copper and zinc from the pure metals and commercial products at marine exposure conditions. Their motive was the increasing concern in various European countries and the on-going risk assessments of copper and zinc within the European commission. Also the circumstance that available runoff rates so far, had been reported for mainly urban exposure conditions, rather than marine. A collaboration was therefore established with the French Corrosion Institute, which runs a marine test site in Brest, and a set of vital questions were formulated. Their answers are the essence of this licentiate study.

Based on the ISO corrosivity classification and one-year exposures, the marine atmosphere of Brest is fairly corrosive for zinc (class C3) and highly corrosive for copper (C4). Despite higher corrosivity classifications for both metals in Brest compared to the urban site of Stockholm, used as a reference site, nearly all runoff rates assessed for copper, zinc and their commercial products were lower in Brest compared to Stockholm. This was attributed to a higher surface wetting in Brest and concomitant higher removal rate of deposited chloride and sulphate species from the marine-exposed surfaces. The comparison shows that measured corrosion rates cannot be used to predict runoff rates, since different physicochemical processes govern corrosion and runoff respectively.

For copper, the runoff rate in Brest was approximately 1.1 g m-2 yr-1 with cuprite (Cu2O) as main patina constituent. During periods of very high chloride and sulphate deposition, paratacamite (Cu2Cl(OH)3) formed which increased the runoff rate to 1.5 g m-2 yr-1. For zinc, with hydrozincite (Zn5(CO3)2(OH)6) as the main patina constituent, the runoff rate was relatively stable at 2.6 g m-2 yr-1 throughout the year, despite episodes of heavy chloride and sulphate deposition.

The application of organic coatings of varying thickness on artificially patinated copper or on different zinc-based products resulted in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. The thickest organic coating (150 µm thick), applied on hot dipped galvanized steel, reduced the runoff rate by a factor of 100. No deterioration of organic coatings was observed during the one-year exposures. Alloying zinc-based products with aluminium resulted in surface areas enriched in aluminium and concomitant reduced zinc runoff rates.

The release rate and bioavailability of copper from different anti-fouling paints into artificial seawater was also investigated. It turned out that the release rate not only depends on the copper concentration in the paint, but also on paint matrix properties and other released metal constituents detected. Far from all copper was bioavailabe at the immediate release situation. In all, the results suggest the importance of assessing the ecotoxic response of anti-fouling paints not only by regarding the copper release, but rather through an integrated effect of all matrix constituents.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 36 p.
Series
ISRN KTH/MSE--06/39--SE+CORR/AVH
Keyword [en]
copper, zinc, marine environment, runoff rate, atmospheric corrosion, chloride deposition, anti-fouling paints, chemical speciation, bioavailability, cupric ions
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4051ISBN: 91-7178-364-4 (print)OAI: oai:DiVA.org:kth-4051DiVA: diva2:10560
Presentation
2006-05-31, Sal Q2, KTH, Osquldas väg 10, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101126Available from: 2006-06-14 Created: 2006-06-14 Last updated: 2010-11-26Bibliographically approved
List of papers
1. Corrosion-induced copper runoff from naturally and pre-patinated copper in a marine environment
Open this publication in new window or tab >>Corrosion-induced copper runoff from naturally and pre-patinated copper in a marine environment
2006 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 48, no 12, 4316-4338 p.Article in journal (Refereed) Published
Abstract [en]

Corrosion-induced copper runoff has been monitored for copper sheet, naturally patinated copper and pre-patinated copper, with and without surface treatments, in a marine environment during one year. The study comprises solution measurements on total copper runoff rates, sulphates and chlorides released from the patina, and parallel surface analytical studies on patina formation, combined with electrochemical impedance measurements on changes in barrier properties during exposure. Bioassay tests and model predictions were applied to elucidate copper bioavailability at the immediate release situation. The runoff rate of copper was significantly lower compared to the corrosion rate throughout the exposure period. At comparable rain quantities, copper runoff rates were significantly 66 lower at the marine site compared to similar data obtained in an urban environment. The bioavailable concentration of released copper was significantly lower compared to the total copper concentration.

Keyword
copper, runoff studies, atmospheric corrosion, chloride deposition, marine environment
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5994 (URN)10.1016/j.corsci.2006.04.004 (DOI)000242766300031 ()2-s2.0-33750620932 (Scopus ID)
Note
QC 20100906. Uppdaterad från In press till Published (20100906)Available from: 2006-06-14 Created: 2006-06-14 Last updated: 2017-12-14Bibliographically approved
2. Corrosion-induced zinc runoff from construction materials in a marine environment
Open this publication in new window or tab >>Corrosion-induced zinc runoff from construction materials in a marine environment
2007 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, no 2, C120-C131 p.Article in journal (Refereed) Published
Abstract [en]

Zinc runoff rates from 11 zinc-based construction materials with and without surface treatments or coatings are presented and discussed in terms of patina formation, seawater deposition, wetting conditions, and changes in corrosion resistance. As opposed to earlier reports, current runoff rates have been assessed in a marine test site (Brest, France) rather than in mainly urban sites. High surface wetting conditions and concomitant removal of deposited chloride and sulfate species are proposed to cause the unexpectedly low zinc runoff rates observed in the marine site, despite a high ISO corrosivity classification for zinc. The average runoff rate for hot dipped galvanized steel after 1 year is 2.9 g m(-2) year(-1) and 100 times lower when coated with two organic layers (150 mu m). Organic coatings of varying thickness (1-150 mu m) result in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. Aluminum alloying also results in reduced zinc runoff rates caused by surface areas enriched in aluminum.

Keyword
Alloying, Aluminum, Building materials, Corrosion, Corrosion resistance, Organic coatings, Seawater corrosion, Surface treatment, Wetting, Zinc
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5995 (URN)10.1149/1.2403078 (DOI)000243380200047 ()2-s2.0-33846204795 (Scopus ID)
Note
QC 20100907. Uppdaterad från Submitted till Published (20100907)Available from: 2006-06-14 Created: 2006-06-14 Last updated: 2017-12-14Bibliographically approved
3. Release and chemical speciation of copper from anti-fouling paints with different active copper compounds in artificial seawater
Open this publication in new window or tab >>Release and chemical speciation of copper from anti-fouling paints with different active copper compounds in artificial seawater
2007 (English)In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 58, no 3, 165-172 p.Article in journal (Refereed) Published
Abstract [en]

Release rates of total copper in artificial seawater (without organic matter) from anti-fouling paints of different active copper compounds range from 0.5 to 75 μg cm-2 day-1. Approximately 80% of the released total copper was determined to be electrochemically active (labile fraction) for all paints investigated. The remaining fraction is more strongly bonded non-bioavailable copper complexes with species released from the paints. Model calculations, using MinteqA2, predicted only a small portion (≈6%) of the total copper released as free cupric ions (Cu(H2O) 62+), the most bioavailable form of copper. Similar results were obtained with bioassay testing using bacteria and yeast on released copper from massive copper sheet exposed at identical conditions. The large difference between the total and the bioavailable copper fraction emphasizes the importance of generating chemical speciation data for accurate decisions of potential adverse effects of copper release from antifouling paints. The observed release of other metals and organic substances from the paint matrix, implies the importance to assess an integrated response from released species from paints of antifouling, and not only from single ingredients.

Keyword
Antifouling paint, Biological materials, Chemical speciation, Copper compounds, Electrochemistry, Seawater
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5996 (URN)10.1002/maco.200604002 (DOI)000245700500001 ()2-s2.0-34547152794 (Scopus ID)
Note
QC 20100928. Uppdaterad från Submitted till Published (20100928).Available from: 2006-06-14 Created: 2006-06-14 Last updated: 2017-12-14Bibliographically approved

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