Abstract
The impact of the chloride ions concentration and the temperature of the circulating water on the process of corrosion destruction of carbon steel and cast iron has been investigated. It has been shown that an increase in the concentration of chloride ions causes a shift in the values of the stationary potentials of steel and cast iron to the region of negative values and reduces the passive state of these alloys. This leads to an increase in the corrosion rate of St.3 steel and CI 18-36 cast iron. The results of electrochemical studies have shown that the more reliable protective films are formed on steel than on cast iron. The limiting concentration of NaCl, at which reliable operation of equipment made from these alloys is possible, depends on the pH of the solution. At pH=7, it is about 1.2 g l -1 , which is about an order of magnitude less than at pH=12. When the circulating water temperature rises, the corrosion rate of steel and cast iron increases. The stationary potentials of steel and cast iron are shifted to the negative range, and the polarization of the anode process decreases. Corrosion process is limited by the rate of oxygen supply to the cathode areas
Highlights
In the water recycling systems of barometric condensers of enterprises, which produce chlorine and sodium hydroxide by the electrolysis method, the basic mineralization of water is determined by the Cl- ions
Data of study [8] have shown that an increase in the concentration of chloride ions leads to a deterioration in the protective properties of a passive film of alloyed chromium-nickel steel
The objective of present study was to investigate the effect of parameters of circulating water on the rate and nature of the corrosive destruction of carbon steel and gray cast iron
Summary
In the water recycling systems of barometric condensers of enterprises, which produce chlorine and sodium hydroxide by the electrolysis method, the basic mineralization of water is determined by the Cl- ions. The main structural materials of the circulating water supply systems are carbon steel of St. grade and gray cast iron of CI 18-36 grade. This is due to their low cost, which is combined with good technological properties. Aggressiveness of chloride ions is explained by the ability to adsorption In this case, oxygen is displaced from the metal surface, which leads to disruption of the continuity of the protective film and increases the rate of its corrosion. Admixtures cause increased mineralization of water, which leads to the acceleration of corrosion destruction of metallic materials of the cooling systems. Creation of closed cycles of recycling water supply, which are able to work with high-mineralized water, will make it possible to solve the following tasks: 1) to reduce the costs related to the processes of discharge and compensation of a large volume of water, which will enable reducing the ecological load on the environment; 2) to reduce the cost of repair and replacement of equipment due to corrosion destruction
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