Corrosion and runoff rates of Cu and three Cu-alloys in marine environments with increasing chloride deposition rate

• Published in: The Science of the total environment 2014-02, Vol.472, p.681-694
• Main Authors: Odnevall Wallinder, Inger, Zhang, Xian, Goidanich, Sara, Le Bozec, Nathalie, Herting, Gunilla, Leygraf, Christofer
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric corrosion; Chloride deposition; Chlorides - analysis; Copper - analysis; Copper alloys; Corrosion; Corrosion environments; Corrosion rates; Environmental Monitoring; Exact sciences and technology; France; Metal release; Metals. Metallurgy; Models, Chemical; Natural water pollution; Patina evolution; Pollution; Rainwaters, run off water and others; Seawater - chemistry; Water Pollutants, Chemical - analysis; Water treatment and pollution
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2013.11.080

Bare copper sheet and three commercial Cu-based alloys, Cu15Zn, Cu4Sn and Cu5Al5Zn, have been exposed to four test sites in Brest, France, with strongly varying chloride deposition rates. The corrosion rates of all four materials decrease continuously with distance from the coast, i.e. with decreasing chloride load, and in the following order: Cu4Sn>Cu sheet>Cu15Zn>Cu5Al5Zn. The patina on all materials was composed of two main layers, Cu2O as the inner layer and Cu2(OH)3Cl as the outer layer, and with a discontinuous presence of CuCl in between. Additional minor patina constituents are SnO2 (Cu4Sn), Zn5(OH)6(CO3)2 (Cu15Zn and Cu5Al5Zn) and Zn6Al2(OH)16CO3·4H2O/Zn2Al(OH)6Cl·2H2O/Zn5Cl2(OH)8·H2O and Al2O3 (Cu5Al5Zn). The observed Zn- and Zn/Al-containing corrosion products might be important factors for the lower sensitivity of Cu15Zn and Cu5Al5Zn against chloride-induced atmospheric corrosion compared with Cu sheet and Cu4Sn. Decreasing corrosion rates with exposure time were observed for all materials and chloride loads and attributed to an improved adherence with time of the outer patina to the underlying inner oxide. Flaking of the outer patina layer was mainly observed on Cu4Sn and Cu sheet and associated with the gradual transformation of CuCl to Cu2(OH)3Cl of larger volume. After three years only Cu5Al5Zn remains lustrous because of a patina compared with the other materials that appeared brownish–reddish. Significantly lower release rates of metals compared with corresponding corrosion rates were observed for all materials. Very similar release rates of copper from all four materials were observed during the fifth year of marine exposure due to an outer surface patina that with time revealed similar constituents and solubility properties. •Atmospheric corrosion of Cu, Cu15Zn, Cu4Sn and Cu5Al5Zn at decreasing coastal distance•Decreasing corrosion rates with decreasing chloride load for all materials•Flaking of outer patina constituents for Cu and Cu4Sn at sites of high chloride load•Significantly lower release rates compared with corrosion rates•Comparable long term release of Cu from the alloys due to similar outermost patina composition