Anode environmental impact

FIGURE 12.2 Examples of situations related to cathodic protection (a) protection currents (b) current interfering with other structures (c) corrosion current and (d) anodic current and potential environmental impact of electric fields on the fauna, the electrophoretic migration of water, the surface alkalinization, the formation... 

Galvanic anodes are extensively used in continuously wetted environments. They need less maintenance than the impressed current systems. One problem with the zinc system is the environmental impact of the during spraying. If enclosure is required during spraying, the costs can be very high. 

Metal ions that are prevalent in industrial effluent and have a considerable environmental impact include Cr(III), Zn(II), and Ni(II) [7]. Waste solutions of these metals are routinely found at levels that are in excess of acceptable disposal limits. Such waste solutions are produced, for example, by electroplating and metal pretreatment [Cr(III), Zn(II), Ni II)], printed board manufacture [Cr(III), Ni(II)], leather tanning and wool scouring [Cr(III)], and anodizing [Cr(III), Zn(II)], among others [7,8]. These three metal ions are studied in detail in this chapter. 

It has been understood that the commercially available anodes are not always suitable to use for wastewater applications because they have drawbacks, such as a limitation of current density due to high IR drops of the electrode, the dissolution of the toxic component of the electrode catalyst with a high environmental impact, and the poor oxidizing power (low overpotential). Thus the expectation for the BDD anode that can overcome these disadvantages becomes greater. 

In 1995, Japan has installed a production facility with an 80-million cell capacity for mass-scale production of practical rechargeable batteries using LiCoOj as the cathodes. These rechargeable batteries are rated at 3.6 V and have demonstrated a density exceeding 350 Wh/liter. Performance improvements have been observed with improvements in the carbon anode, electrolyte, and cathode materials. Battery scientists may deploy lithiated oxides of nickel and manganese on the basis of cost reductions and reduced environmental impact. 

Kvande, H., Haupin, W. (2001) Inert anodes for aluminium smelters energy balances and environmental impact. JOM, 50 (5), 29-33. 

In case of aluminum, a pretreatment is necessary to achieve a long-term-corrosion-resistant adhesion. Whereas in the aerospace industry, anodizing processes are state of the art, automotive industry has been looking for more cost-effective solutions. A Cr (VI) passivation provided the best results and is now used as benchmark for new chrome-free pretreatments necessary due to the environmental impact of chrome. The best and most cost-efficient results are reached with a passivation of the aluminum in a coil coating process. But this implies that the lubricants needed for the drawing of the aluminum sheets is compatible with the adhesive. Otherwise a separate washing process of the stamped parts would be necessary which is not really economic. A new article from Rechner et al. (Rechner et al. 2010) discusses different surface pretreatments. 

Features Patented multifunctional blend of anodic and cathodic inhibitors does not rely on Zn for protection fully compat. with oxidizing microbiocides such as Cl and Br as well as nonoxIdIzIng microblocldes Pmperties Cl. amber liq. sp. gr. 1.2 f.p. 4 C pH (neat) 12.6 Environmental Biodeg. low environmental impact from treated cooling tower water discharge... 

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