Reasons for crack formation at the weld seam of the alkali solution line
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Half a year after the operation of our alkali solution line, some welds in the pipeline cracked; it’s not clear whether it was due to the quality of the pipeline material or the welding electrodes. Please ask the experts to help analyze it
There was once a leak in the first section of piping of our desulfurization alcohol system, due to issues with the welding quality between the piping and its support frames.
1. It is indeed a welding quality issue... 2. There is a potential difference at the weld area, which leads to chemical reactions or electrochemical corrosion under alkaline conditions... resulting in cracking... :lol
Hot alkali accumulates in the weld gap of the butted pipes, which can easily cause leakage. An outer pipe sleeve can be used, or sub-arc welding can be employed as a base layer to eliminate the gaps at the butted pipe ends.
There may also be a principle of alkali stress corrosion as follows: The stress corrosion cracking induced under alkaline conditions proceeds according to the following reactions: Fe + 4OH– → FeO22– + 2H2O + 2e–; 3FeO22– + 4H2O → Fe3O4 + 6OH– + H2. As a result of these reactions, a protective film of ferric oxide is formed on the surface. The membrane is damaged under stress, and then passivation occurs to repair the membrane; when these two processes are in balance, stress corrosion cracking of the anodic type takes place.
I was wondering if anyone has any good solutions. Our workshop has decided to replace this section of pipeline; I’m not sure what material would be suitable to prevent such accidents from occurring