Study on Localized Corrosion Between Oxides Dissolution and Substrate Material in the Process of Chemical Cleaning for Superheaters

doi:10.11930/j.issn.1004-9649.201702022

Abstract

Abstract: Localized electrochemical corrosion may take place at region of oxide exfoliation or cracking in the process of chemical cleaning for superheaters. After the chemical cleaning process, the corrosive pits over 400 μm deep are detected on both cut superheater samples and simulated testing tubes, especially in iron steel such as T22, 12Cr1MoV and T91. The monitoring evaluation and corrosion control technology are carried out through the electrochemical corrosion test device.Three kinds of superheater tube samples are selected, such as T22, 12Cr1MoV and T91, and the corrosion current density between the intact oxidation tube electrode and the bare metal electrode during the oxidation skin cleaning process is measured. The change of corrosion current density after the addition of reductant is investigated by contrast test. It is shown that the local corrosion rate during chemical cleaning of the exfoliated parts of the materials used in the experiment is tens times of the standard values, which can be controlled by adding ascorbic acid in time.

Key words: power plant, superheater, oxide, exfoliation, chemical cleaning, localized corrosion, reducing agent

CLC Number:

DENG Yuqiang, YE Zhi, QI Dongdong, ZHANG Shaoyong, ZHANG Xiaoping, CAI Guobao, WANG Sipu, ZHANG Tongtong. Study on Localized Corrosion Between Oxides Dissolution and Substrate Material in the Process of Chemical Cleaning for Superheaters[J]. Electric Power, 2018, 51(5): 123-127,146.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.201702022

https://www.electricpower.com.cn/EN/Y2018/V51/I5/123

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