| 1. |
- Ha, H., et al.
(författare)
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Effects of selected water chemistry variables on copper pitting propagation in potable water
- 2011
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 56:17, s. 6165-
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Tidskriftsartikel (refereegranskat)abstract
- The pit propagation behavior of copper (UNS C11000) was investigated from an electrochemical perspective using the artificial pit method. Pit growth was studied systematically in a range of HCO 3 -, SO 4 2- and Cl - containing-waters at various concentrations. Pit propagation was mediated by the nature of the corrosion products formed both inside and over the pit mouth (i.e., cap). Certain water chemistry concentrations such as those high in sulfate were found to promote fast pitting that could be sustained over long times at a fixed applied potential but gradually stifled in all but the lowest concentration solutions. In contrast, Cl - containing waters without sulfate ions resulted in slower pit growth and eventual repassivation. These observations were interpreted through understanding of the identity, amount and porosity of corrosion products formed inside and over pits. These factors controlled their resistive nature as characterized using electrochemical impedance spectroscopy. A finite element model (FEM) was developed which included copper oxidation kinetics, transport by migration and diffusion, Cu(I) and Cu(II) solid corrosion product formation and porosity governed by equilibrium thermodynamics and a saturation index, as well as pit current and depth of penetration. The findings of the modeling were in good agreement with artificial pit experiments. Malachite, bronchantite, cuprite, nantokite and atacamite corrosion products were both observed in experiment and predicted by the model. Stifling and/or repassivation occurred when the resistance of the corrosion product layer became high enough to lower the pit bottom potential and pit current density such as 10 -5 A/cm 2 could be attained with thick and dense layer. The ramifications of these findings towards pit propagation characteristics in potable waters will be discussed with improved insight into the roles of Cl - and SO 4 2- ions. © 2011 Elsevier Ltd. All Rights Reserved.
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| 2. |
- Prosek, Tomas, et al.
(författare)
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Low temperature stress corrosion cracking of stainless steels in the atmosphere in presence of chloride deposits
- 2008
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Ingår i: NACE - Int. Corros. Conf. Ser.. ; , s. 084841-0848417
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Konferensbidrag (refereegranskat)abstract
- Several cases of ceiling collapses and other failed elements have been reported in indoor swimming pool halls in the last two decades. The collapses were caused by stress corrosion cracking (SCC) of stainless steel fastening elements made of grades UNS S30400, S31600, or similar. It was shown that this phenomenon can occur under specific conditions beneath chloride deposits at temperatures as low as the room temperature. The aim of this study was to assess the application limits of different austenitic and duplex stainless steel grades subject to tensile stress and contaminated with chloride deposits in the atmosphere under non-washing conditions as a function of temperature (20-50 °C), relative humidity (15-70 % RH), and deposit composition. Austenitic stainless steel grades UNS S30400 and S31603 were susceptible to SCC in the presence of magnesium and calcium chlorides at temperatures from 30 °C and at low relative humidity. The tendency to SCC increased with increasing temperature and decreasing relative humidity. The corrosivity of salt at given exposure conditions decreased in the following order CaCl2 > MgCl2 > FeCl3 > NaCl. The corrosivity of chloride deposits was governed by the equilibrium chloride concentration in the surface electrolyte formed as a result of interaction of given chloride salt and air at given relative humidity. Threshold values of the minimum chloride concentration and relative humidity intervals leading to SCC at 30 and 40 °C were established for UNS S30400 and S31603. Duplex stainless steels S32101, S32304, S32205, and S32750 corroded selectively to the maximum depth of 380 μn. Austenitic stainless steels N08904 and S31254 showed no tendency to SCC.
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| 3. |
- Prosek, Tomas, et al.
(författare)
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Low-temperature stress corrosion cracking of stainless steels in the atmosphere in the presence of chloride deposits
- 2009
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Ingår i: Corrosion. - : National Assoc. of Corrosion Engineers International. - 0010-9312 .- 1938-159X. ; 65:2, s. 105-117
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Tidskriftsartikel (refereegranskat)abstract
- Several cases of ceiling collapses and other failed elements have been reported in indoor swimming pool halls in the last two decades. The collapses were caused by stress corrosion cracking (SCC) of stainless steel fastening elements covered with chloride deposits at temperatures as low as room temperature. The goal of this study was to assess the application limits of different austenitic and austenitic-ferritic (duplex) stainless steels subject to tensile stress and contaminated with chloride deposits in atmospheric non-washing conditions as a function of temperature (20°C to 50°C), relative humidity (15% to 70% RH), and deposit composition. Austenitic stainless steels Type 304 (UNS S30400) and Type 316L (UNS S31603) were susceptible to SCC in the presence of magnesium and calcium chlorides at temperatures of 30°C and higher and at low relative humidity. The tendency to SCC increased with increasing temperature and decreasing relative humidity. The corrosivity of chloride deposits under given exposure conditions decreased in thefollowing order: calcium chloride (CaCl2) > magnesium chloride (MgCl2) > sodium chloride (NaCl). It was governed by the equilibrium chloride concentration in the surface electrolyte formed as a result of interaction of a given salt with water vapor in the air. Threshold values of the minimum chloride concentration and relative humidity intervals leading to SCC were established for Type 304 and Type 316L. Duplex stainless steels S32101 (UNS S32101), 2304 (UNS S32304), 2205 (UNS S32205), and 2507 (UNS S32750) were resistant to SCC but corroded selectively with the maximum depth of 200 μm. Austenitic stainless steels Type 904L (UNS N08904) and Type S31254 (UNS S31254) showed no tendency to SCC.
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