The evaluation of corrosion rate of steel during chemical cleaning of steam boilers

Abstract

Traditional and new washing acid reagents are used for chemical cleaning of internal surfaces of steam-water pipes of boilers. In previous studies, the rate of removal of lumpy and uniform deposits in the evaporative pipes of high-pressure steam boilers depending on the type of cleaning solution and the duration of cleaning was obtained. However, during chemical cleaning, removing deposits is accompanied by corrosion processes of the metal pipes, which leads to their loss. In the scientific and technical literature there are practically no data characterizing this process when using new detergent reagents. The aim of the study is to obtain experimental data on the corrosion rate of steels during the acid stage of chemical cleaning with the use of new cleaning reagents such as Antirzhavin, Deskam and Auge Pro AC 60. The gravimetric method of determination of metal corrosion rate of evaporative pipes is used. The samples of corrosion in cold and heated washing solutions during chemical cleaning from deposits by etching are employed. The laboratory testing has revealed the dependences of corrosion rate of carbon steel of boiler evaporative pipes and corrosion indicating plates in heated and not heated washing solutions of the inhibited hydrochloric acid and acid reagents on cleaning duration. It has been found that the corrosion rates of carbon steel are reduced during the cleaning process and at the end of the acid stage in solutions of inhibited hydrochloric acid and reagent solutions have values exceeding the maximum permissible corrosion rate in a cold inhibited technical solution of hydrochloric acid. However, they are less than those for pure metal and metal with scale. The experimental data obtained can be used in the selection of a chemical reagent for acid cleaning and its optimal duration, as well as in the selection of the method of steel corrosion control during cleaning.