지역난방 시스템의 순환수에 따른 보일러 튜브의 부식 특성

Abstract

In this study, corrosion behavior of a SA178-A alloy used in the boiler tube of a district heating systemwas investigated in different environments where it was exposed to pure water, district heating (DH) water,and filtered district heating (FDH) water. After the corrosion test, the surface morphology was examinedfor observation of the number of pitting sites and pitting area fraction, using a scanning electron microscope. The DH water and FDH water conditions resulted in a lower corrosion potential and pitting potential, andrevealed a significantly higher corrosion rate than the pure water condition. The pitting sites in the DHwater (pH 9.6) were approximately eighteen times larger than those in the pure water (pH 9.6). Comparedto the DH water, the corrosion potential became more noble in the FDH water condition, where iron ionswere reduced through filtration. However, the corrosion rate increased in the FDH water due to an increasedconcentration of chloride ions, which deteriorated the stability of passive film.