Research On Migration Patterns Of Corrosion Of Water-steam System In Power Station

In terms of power generation, the higher operation parameters of the water medium result in the higher energy conversion efficiency, however, meanwhile the increased risk of vapor circulating system for the coal fired power unit arise. Parameters of the water medium in vapor circulating system have an effect on corrosion occured over different position of boiler. This paper analyzes the previous research in this field, and research corrosion performance of power station metal materials and corrosion products which come from migration process in vapor circulating system, by calculating the potential-pH diagrams and soda corrosion experiments, and qualitative analysis the effect trend, it has profound guiding significance for chemical water treatment.The migration process of the water-steam system corrosion at the high temperature water segment is mainly magnetite formation, dissolution and deposition process, and is controlled by formation rate and dissolution rate of magnetite. The dissolution of magnetite is reductive dissolute, and the lysate migration in the system in the form of Fe2+. Deposition of corrosion occurs in the evaporator section of the boiler tubes. Improve hydraulic qualitative pH value or redox potential can be effectively suppressed the dissolution of magnetite, thereby retard the migration process of corrosion of the water-steam supply system. The deposition of magnetite is mainly divided into the deposition of soluble iron ion and the deposition of magnetite particles. When the temperature is increased, the solubility of the iron is reduced, the soluble iron ions is deposited on the duct wall. Water chemistry (pH and ORP) also affect the solubility of magnetite.Corrosion reaction interface mainly consists of two parts of the solid-liquid interface and solid-solid interface. The stable region of the respective components is constantly changing with the temperature increasing. Fe2+can be hydrolyzed soluble FeOH+, the pipeline metal corrosion process changes. When the hydraulic quality changes into supercritical, water-steam corrosion process changes again. Reaction interface changes into a solid-solid interface accounted dominated from the high-temperature water environment of solid-liquid interface and solid-solid interface. Alloy corrosion products in supercritical water environment at magnetite stable region in the E-pH diagram, and corrosion process is controlled by the diffusion process of the ions in the oxide film and the corrosion potential of the metal. For the lower supercritical unit water-steam corrosion, there may be present vintage oxygen content. The presence of oxygen promotes the formation of a protective oxide film, but the long-term presence of the excess of oxygen will accelerate the formation and development of the pores of the oxide layer.