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Effect of dielectric composition on performance of sacrificial anode
Sep 01, 2017

        It is well known that the commonly used sacrificial anodes include magnesium anodes, aluminum anodes, and zinc anodes for cathodic protection, but do you know? Different media, the performance of sacrificial anode is not the same, the following and we introduced respectively, zinc, magnesium, aluminum based anode by different media medium, what changes in performance?


Effect of dielectric composition on performance of sacrificial anode

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Zn based anode: standard potential of -0.762 V (VS.SHE), theory of electricity in 0.82. / g, PH<7 to Zn2+, PH>11 to Zn022- dissolution, more than two area is the corrosion zone, formation of PH=8~11 Zn (0H) 2 in the passive region, including HCO3-, NO3-, CO32- solution, Zn potential is shifted sharply and with high concentration SO42-, Zn anode returned to more negative potential, see Figure 1, figure 2.

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Figure 1 bicarbonate enriched environment, high concentration of sulfate adding effects on Zn anode potentials

 

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When the environment was added to gypsum, the CaSO4 immediately shifted rapidly.

Fig. 2 Effect of gypsum CaSO4 on the Zn anodic potential in the original environment

 

Mg based anode: standard potential -2.37 volts (VS.SHE), theoretical generation of electricity 2.21, an hour / gram, PH<12, to the presence of Mg2+ is the corrosion zone, PH>12 generated Mg (OH) 2, in the passivation area. With the increase of SO42- concentration, the potential shifted negatively, and the efficiency of the anode decreased with the addition of NaCL. When the soil resistivity is less than 10.M, PH = 4 should not be using Mg anode. For use in phosphate and carbonate soils, caution may be directed against possible anodic passivation.

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AL based anode: standard potential -1.66 volts (VS.SHE), the theoretical generation of electricity 2.93, an hour / grams, PH<4 to AL3+ exists, PH>8 dissolved in ALO2- form, the above two areas for corrosion, PH=4~8 generated AL2O3, in the passivation area. Surface dissolved in acidic and alkaline medium. In solution, SiO32- and SO42- can make AL passivation. In addition, anions such as CrO42-, NO3- and CLO4- can also make AL passivation, CL- destroy passivation, and the addition of chloride salt, such as MgCL2 or NaCL, can activate AL anode. Therefore, the composition of AL anode filling material is completely different from that of Zn and Mg anode filling materials, and the chemical composition of the activated anode should be considered in application. From this we can see that the AL anode is suitable for working in seawater.

           And then share the knowledge of the anode packing material and the ribbon magnesium anode. For more information on sacrificial anodes , please contact us

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