Chlorinated seawater

Water Tests. In colorfastness to water, ISO 10S-E01, the test specimen is placed in contact with the chosen adjacent fabrics, immersed in water, and placed wet between glass plates and left for 4 h at 37°C. After drying, the effect on the test specimen and stain on adjacents are assessed. The test, colorfastness to seawater, ISO 10S-E02, is the same as EOl but uses 30 g/L anhydrous sodium chloride solution instead of water. To test for colorfastness to chlorinated seawater/swimming baths water, ISO 10S-E03, the specimen is immersed in sodium hypochlorite solution containing either 100, 50, or 20 mg of active chlorine per Hter at pH 7.5 for 1 h at 27°C, rinsed, dried, and assessed. 

A typical polarographic recording is shown in Fig. 2.1 curve (a) is the po-larogram obtained for chlorinated seawater analysed immediately after chlorination. Identical traces were observed for non-chlorinated seawater and for chlorinated seawater kept in the dark for periods up to 24 h at temperatures up to 40 °C, which indicates a lack of bromate formation under these conditions (BrC>3 < 10 7 M, less than 0.5% conversion of chlorine). Addition of copper sulfate to give a cupric ion concentration in the seawater of 100 parts per billion did not induce measurable bromate production in the dark. Curve (b) was obtained from a chlorinated (4.9 mg/1) seawater solution that was exposed to full sunlight for 70 min. Curve (c), which is offset by 0.4 pA with respect to curves (a) and (b), shows the presence of 1.0 x 10 5 M sodium bromate in seawater. 

Figure 2.2 illustrates kinetic data for the appearance of bromate (Fig. 2.2a) and disappearance of residual oxidants (Fig. 2.2b) in chlorinated seawater ex-... 

Figure2.2. (a) Disappearance with time of residual oxidants and(b) concomitant appearance of bromate in chlorinated seawater (4.2-4.9 ppm of chlorine) as a function of exposure to sunlight. The conditions were Curve (a) full midday sunlight, Curve (b) 65% of full sunlight, and Curve (c) overcast, 20% of full sunlight. Curve (d) shows residual oxidant disappearance in the dark at 40 0 C. No bromate production was observed in the dark. From [ 19]... 

Kristiansen et al. [232] identified halogenated hydrocarbon byproducts in chlorinated seawater. 

Kristiansen et al. [232] identified halogenated hydrocarbon byproducts in chlorinated seawater used for drinking water. Phenol, cresols, and catechols were present at low-ppb concentrations in San Diego Bay (CA, USA) [373]. 

It has many other uses as an abrasive, as an ingredient of cements, and as a paint pigment in the oxide form and in the paper and ink industries, in batteries for space vehicles, and wherever a metal is needed to resist chlorine (seawater) corrosion. 

In a related case, FT-30 membrane elements were placed on chlorinated seawater feed at OWRT s Wrightsville Beach Test Facility. Flux and salt rejection were stable for 2000 hours at 0.5 to 1.0 ppm chlorine exposure. Chlorine attack did become noticeable after 2000 hours, and salt rejection had dropped to 97 percent at 2500 hours while flux increased significantly. Long term laboratory trials at different chlorine levels led to the conclusion that the membrane will withstand 0.2 ppm chlorine in sodium chloride solutions at pH 7 for more than a year of continuous exposure. 

Bromine is isolated from sea water by air-blowing it out of chlorinated seawater. 

Macalady, D. L., J. H. Carpenter, and C. A. Moore. 1977. Sunlight-induced bro-mate formation in chlorinated seawater. Science 195 1335-1337. 

Ignored by most implementations of the CCS framework, ohmic drop can not only lead to passive-to-active transitions, but also can, in the context of environmental cracking, make hydrogen evolution, and therefore embrittlement, more viable at the crack tip. The IR framework has been successfully demonstrated in several model metal/environment systems [34, 35], and has been invoked to rationalize the practically important case of the crevice corrosion of Alloy 625 in chlorinated seawater [32, 33]. 

Figure 6.16 Smoothed cathodic overvoltage curves for a high-alloy stainless steel in aerated and chlorinated seawater at 25 C (From Gartland and Drugli [6.34]).

Gartland PO, Drugli JM. Methods for evaluation and prevention of loeal and galvanie eorrosion in chlorinated seawater pipelines. Corrosion/92, Paper No 408, NACE, Houston, Texas, 1992. 

The latter steels have been developed during the last few decades. (For compositions, properties and standard numbers, see Table 10.6.) A benefit of the ferritic-austenitic steels is their higher strength compared with the austenitic. Ferritic-austenitic 25-7-4 steel and austenitic 20-18-6 have both shown very good crevice corrosion properties in seawater, but also on these steels attacks may develop when the temperature is above a limit that depends on various conditions. Of these two steel types, the ferritic-austenitic steel may have somewhat lower corrosion resistance in welds than the austenitic 6 Mo steel. With first-class welds, pipes made of the latter material are considered safe to use up to 30-35°C in seawater. However, on flanges that are cast or produced by powder metallurgy, attacks have been found at a temperature as low as 10-15°C. For use in chlorinated seawater with a residual chlorine content of 1.5 ppm, the NORSOK standard [10.10] recommends a maximum temperature of 15°C for components with crevices and 30°C for... 

For pipe systems of stainless steel carrying chlorinated seawater, internal localized corrosion can be very efficiently prevented by the application of Resistance-controlled Cathodic Protection (RCP). A resistance is simply inserted between the sacrificial anode and the pipeline, and this makes a system that is particularly suitable when there is a low diffusion-limiting cathodic current in the critical potential range [10.29]. Typical of the method is that the current output from the anode is kept low, which has the consequence that the voltage drops are low and the protected pipe length from each anode is long. 

Steinsmo, U., Rogne, T., Dmgli, J. A., and Gartltind P. O., High Alloyed Stainless Steels for Chlorinated Seawater Applications—Critical Crevice Temperatures, Engineering Solutions to Industrial Corrosion Problems, NACE International, Sandefjord, Norway, 1993. 

Klein, P. A., Ferrara, R. J., and Kain, R. M., Crevice Corrosion of Nickel-Chromium-Molybdenum Alloys in Natural and Chlorinated Seawater, Paper 112, CORROSION/89, NACE International, Houston, TX, 1989. 

Kristiansen NK, Froshaug M, Aune KT et al (1994) Identification of halog ated compounds in chlorinated seawater and drinking-water produced offshore using n-ptmtane extractitm and open-loop stripping technique. Environ Sci Technol 28 1669-1673... 

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