# The Corrosion Failure Mechanism of a Peak Load Boiler in a District Heating System
## 4 Conclusions  
In the present study, the causes and mechanisms of corrosion failure of the peak load boiler have been investigated and analyzed through experiments and simulations. The followings are the main conclusions drawn:  
1. Severe localized corrosion and progressive leakage were observed near the turbulator in the leaking peripheral tube. Corrosion damage was particularly concentrated in the upper section near the turbulator, where accumulated corrosion products indicate sustained material degradation. Initially, corrosion was concentrated at 90\({}^{\circ}\) relative to the manhole, but as acidic condensation accumulated, degradation gradually propagated along the gas flow path. 2. Water quality analysis and corrosion product characterization identified ammonium (NH4\({}^{+}\)), nitrate (NO3\({}^{-}\)), sulfate (SO4\({}^{2-}\)), sodium (Na\({}^{+}\)), and chloride (Cl\({}^{-}\)) as key contributors to corrosion scale and salt formation. These ions primarily originated from combustion gas and vaporized boiler water, forming a highly acidic and chloride-rich electrolyte environment that significantly accelerates carbon steel corrosion. 3. Computational fluid dynamics (CFD) simulations confirmed that vaporized boiler water entrained in the combustion gas could reach dew-forming temperature ranges along the tube wall. The upper section of the tube, where the turbulator is installed, exhibited lower gas temperatures, increasing the risk of acidic condensation. This  
Figure 12: Corrosion and failure mechanism of the PLB. temperature gradient promoted dew formation and localized acid accumulation, exacerbating corrosion. 4. The corrosion mechanism is linked to the combined effect of water vapor condensation and gas flow dynamics. During operation, vaporized water from leaks mixes with the combustion gas and accumulates near the tube's upper section. As the temperature drops below the dew point, strong acidic ions are formed and accumulated at this location, which accelerates corrosion process and leads to subsequent secondary failures. Challenges in direct intervention during operation limit the ability to mitigate corrosion progression. Since internal leakage cannot be addressed until scheduled overhauls, corrosive species continue to accumulate, leading to widespread material degradation before maintenance can be performed. This highlights the necessity of proactive monitoring and preventive strategies to mitigate dew point corrosion in PLB systems. Implementing real-time monitoring techniques and optimizing boiler water chemistry management could significantly reduce corrosion risks and extend the operational lifespan of these systems. M.J.S., Writing--original draft, Investigation, Formal analysis; W.C.K., Methodology, Resources; S.Y.L., Writing--review and editing, Supervision, Funding acquisition. All authors have read and agreed to the published version of the manuscript. This work was supported by the Korea District Heating Corporation and partially supported by a National Research Foundation (NRF) grant funded by the Korean government (RS-2024-00398068, RS-2023-NR077179). Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. The authors would like to thank [PERSON], [PERSON], and [PERSON] for their help on experiments. Author [PERSON] was employed by the company Korea District Heating Corp. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] Failure analysis of boiler economizer tubes at power house. _Eng. Fail. Anal._**2019**, _104_, 1203-1210. [CrossRef]
* _[PERSON] et al. (2019)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Stress corrosion cracking of heat exchanger tubes in district heating system. _Corros. Sci. Technol._**2019**, _18_, 49-54. * [PERSON] et al.