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Selected Application Recommendations Sodium Hypochlorite When activated, sodium hypochlorite generates hypochlorous acid and hypochlorite ions which afford oxidation. Unstable solutions can decompose to form mono -atomic or nascent chlorine compounds which are exceptionally aggressive. Decomposition can be induced by high temperature, low pH, or UV radiation. Best stability is maintained at temperature no greater than 125° F and a pH of >10.5. This will often happen if over -chlorination is used in the production of sodium hypochlorite. Over -chlorination makes temperature and pH control very difficult and can result in rapid deterioration and loss of service life of the hypochlorite generator. Adding chlorine gas to the hypochlorite generator can cause mechanical stress, so attention should be given to velocity, thrust, and other forces which the generator may encounter. Composites intended for outdoor service should contain a UV absorbing additive and a light colored pigment in the final exterior paraffinated topcoat to shield the hypochlorite solution from exposure. Thixotropic agents based on silica should never be used in the construction of composite equipment or in topcoats intended for hypochlorite service. Attack can be severe when these agents are used. Chlorine Dioxide Chlorine dioxide now accounts for about 70% of worldwide chemically bleached pulp production and is finding growing applications in disinfection and other bleach applications. Use is favored largely by trends toward TCF (totally chlorine free) and ECF (elemental chlorine free) bleaching technology. Composites made with high performance resins have been used with great success for bleach tower upflow tubes, piping, and C1O2 storage tanks. Chlorine dioxide in a mixture with 6-12% brown stock can be serviced at a temperature up to 160° F. Higher temperature can be used, but at the expense of service life. Under bleaching conditions the resin surface may slowly oxidize to form a soft yellowish layer known as chlorine butter. In some cases the chlorine layer forms a protective barrier which shields the underlying composite from attack. However, erosion or abrasion by the pulp stock can reduce this protective effect. DION® 6694, a modified bisphenol-A fumarate resin displays some of the best chemical resistance to chlorine dioxide. Chlor -Alkali Industry Chlorine along with sodium hydroxide is co-produced from brine by electrolysis, with hydrogen as a byproduct. Modern high amperage cells separate the anode and cathode by ion exchange membranes or diaphragms. Cells can operate at 200° F or higher. Wet chlorine collected at the anode can be aggressive to many materials, but premium corrosion resistant composites have a long history of successful use. One of the best resins to consider is DION® 6694, which was one of the original resins designed to contend with this challenging application. A major concern with chlorine cells is to avoid traces of hypochlorite, which is extremely corrosive at the temperatures involved. Hypochlorite content is routinely monitored, but tends to form as the cell membranes age or deteriorate, which allows chlorine and caustic to co -mingle and consequently react. Ozone Ozone is increasingly used for water treatment as well as for selective delignification of pulp. Ozone is highly favored since it is not a halogen and is environmentally friendly. It is generated by an electric arc process, and in the event of leaks or malfunctions, the remedy can be simply to stop electrical power. The oxidizing potential of ozone is second only to that of fluorine, and this makes ozone one of the most powerful oxidizing agents known. Even at 5 ppm in water, ozone is highly active and can attack the surface of composites. Attack is characterized by a gradual dulling or pitting. At <5 ppm a reasonable service life is expected, but at higher concentrations (10-30 ppm) serious erosion and degradation can occur. This requires frequent inspection and eventual re -lining.