Vasyliev G. Complex provision of corrosion-safe operation of heat and water supply systems of residential and utility infrastructure

The work is aimed at solving the scientific and technical problem of reliable and efficient operation of drinking water supply and municipal heat supply of housing and communal infrastructure by reducing the corrosion destruction of pipelines and reducing scale deposition in heat exchange equipment. The problem is solved by introducing an alternative approach to water treatment in heating networks by dosing reagents of complex action based on corrosion monitoring data, increasing the efficiency and reliability of plate heat exchangers of heat points by applying ultrasonic vibration and increasing corrosion resistance of hot water supply systems. The relationship between the phase composition of corrosion products, steel operating conditions and electrochemical activity has been demonstrated. It is determined that electrochemically active corrosion products are formed in cold tap water, which leads to inflated corrosion rate data using polarization measurement methods. The share of electrochemically active corrosion products decreases with increasing water temperature and flow rate, due to the predominant formation of electrochemically inert precipitates of calcium carbonate. The possibility of control over the electrochemical activity of steel corrosion products and its influence on the determination of polarization resistance by the magnitude of the electrode potential is shown. Antiscalant and anticorrosive properties of plant extracts: rapeseed, fodder radish and sugar beet have been studied. It was found that all three studied extracts are able to reduce the rate of corrosion, but only radish extract reduces scale formation by 78.7% and corrosion process by 75%. It has been shown for the first time that the application of ultrasonic vibration with a frequency of 28 kHz and 1.2 W to the end face of a steel plate made of AISI 304, 316 steel 0.4 mm thick shifts the pitting potential by at least 120 mV anode and reduces the dissolution rate pitting area up to 30 times. The mechanism of repassivation of pitting under the action of ultrasonic vibration is determined, which consists in removal of corrosion products over pitting zones due to deterioration of their adhesion to the vibrating surface. Detachment of corrosion products occurs when the force of inertia, which appeared under the action of vibration, exceeds the force of adhesion. The movement of the electrolyte caused by vibration leads to a further weakening of the adhesion of corrosion products and promotes the penetration of fresh oxygen-saturated electrolyte into the pit, which leads to rapid repassivation of the active metal. The mode of operation of the hot water supply system to minimize corrosion processes is determined. To reduce the corrosion rate of low-carbon steel in hot water supply systems, the water velocity should be maintained above 0.3 m / s, and the volume of water collection of the hot water supply system should be at least 30% of the system volume per hour. Under these conditions, crystalline precipitates of iron oxohydroxide are formed on the surface of the steel, which act as a barrier for oxygen to reach the surface and the rate of corrosion of the steel is reduced. The influence of flow distribution at pipe connection on the occurrence and localization of differential aeration pairs is theoretically substantiated and experimentally confirmed. It was found that the smallest influence of differential aeration pairs is observed at a flow rate of 0.3 m / s, and the coefficient of water distribution between the main and side channel at the pipe connection is 1 : 1 and above. It is shown that the area of cathodic protection in the anodic dissolution of the magnesium electrode in the pipelines of hot water supply systems extends 10-15 cm from the anode. The rest of the surface of the pipelines is protected from corrosion by raising the pH of the solution and the formation on the corroding surface of the metal stable layers of carbonate sediments that prevent access of oxygen to the surface. The main results of the work are introduced in the normative documents: change N.1 from 01.01.2018 in DBN B.2.5-39: 2008" Engineering equipment of buildings and structures. External networks and structures. Heating networks ".