Effect and effective distance of rust and scale suppression by zinc device in piping

The electrical connection between zinc metal and iron in contact with water prevents oxidation of iron until all zinc is dissolved, which is called a zinc sacrificial anode phenomenon. In the case of water pipes, zinc is often attached to the outside of the pipe, but examples of mounting zinc inside the pipe to prevent iron corrosion are not well known. Zinc devices sold for water pipes vary in the amount of zinc installed depending on the diameter of the pipe and the conditions of use, but the life of the product is generally expected to be 10-20 years until all zinc dissolves and disappears. Zinc ions dissolved from zinc to water in the pipe react with the calcium carbonate scale generated inside the pipe to consume zinc ions, and it was confirmed that the needle-shaped aragonite was converted into highly crystalline calcium after observing the scale crystal through an electron microscope. In addition, it is estimated that calcium ions of scale are replaced by zinc ions, gradually losing crystallinity, being deintercalated into the pipe, and oxygen in the water is consumed during the dissolution of zinc ions from zinc metals, turning red rust hematite (Fe2O3) into magnetite (Fe3O4). In addition, zinc ions were expected to move hundreds to thousands of meters depending on the diameter of the pipe in the new pipe, but it was confirmed that the travel distance was shortened in the case of pipes with many corrosion products

아연 이온화 장치에 의한 상수배관 내 스케일 및 녹 생성 억제효과 실증 연구

Scale and rust generation in water pipes is a common phenomenon when cast iron water pipes have been used for a long time. A physical water treatment device is known among various means for suppressing rust in a water pipe, and a zinc ionization device for putting zinc metal into a pipe and emitting the zinc cation into water is one of such devices. This research measured the amount of zinc ion generated, which is known to exhibit an effect of inhibiting rust and scale generation in a pipe, and examined the scale and rust inhibition effect of the ionization device installed for ground or building water supply. In the case of distilled water, the concentration of zinc ion increased by circulating water in the ionization device several times, and it was verified to be hundreds of μg/L, and in the case of discharging ground or tap water, it was verified to be tens of μg/L. In addition, a verification pipe was installed to confirm the change inside the pipe before and after installation of the zinc ionization device, and the internal condition of the pipe was observed 3 months to several years after installation. It was confirmed that the corrosion area of the surface of the pipe was no longer increased by installing a corrosion inhibitor, and if the pipe was already filled with corrosion products, the amount of corrosion products gradually decreased every year after installation. The phenomenon of fewer corrosion products could be interpreted as expanding the space in the pipe due to the corrosion product as Fe2O3 adhered to the inner surface of the pipe and turned into a smaller black Fe3O4. In addition, we found that scale such as CaCO3 together in the corrosion by-products gradually decreased with the attachment of the ionization device

Measurement on the Effect of Inhibiting and Removing Calcium Carbonate Scale in Water by Zinc Ionizing Device

Scale inhibition effect of the physical water treatment device that emits zinc cation in water was evaluated. The inhibition effect of scale formation was confirmed by the difference in precipitation amount of calcium carbonate prepared from calcium chloride and sodium carbonate solution with distilled or zinc ionized water. For measuring removal effect of solid calcium carbonate on the filter paper, the ground water passed through the ionizer or not was poured on the filter paper and the differences of weight loss of solid CaCO3 were observed. In the experiments for inhibition, the addition of zinc ion did not appear to change the amount of calcium carbonate precipitate. On the other hand, zinc ion leaving the filter clumped fine calcium carbonate particles to increase turbidity, and it was estimated that scale particles expected to have grown by zinc ions were discharged by water flow. Although the concentration of zinc ions from the ionization device is only tens of ㎍/L, the exposure of zinc ions for a long period of time was expected to slowly release the scale generated on the inside wall of the pipe