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Stainless steel process pipeline rust near the weld and treatment methods

Stainless steel process pipeline rust near the weld and treatment methods

Time:2022-03-18 Source:China Wuxi JiaNuo Special Steel Co.

Stainless steel process pipeline rust near the weld

A domestic site is being installed equipment, which has 0r18Ni10 stainless steel process piping and joints. After welding, stored in the site warehouse near the marine atmosphere for less than a month, there was a serious yellow-brown rust near the weld seam,

Microscopic inspection, welding heat affected zone C2C6 carbide precipitation, but intergranular corrosion test shows that, because the pipe is ultra-low carbon 018N10, so there is no intergranular corrosion exists. According to the microscopic examination of the rust layer, the rust layer also has an obvious three-layer structure.

The results of the chemical composition analysis (OSCE) of the three-layer structure. From these results, it is clear that both layers A and B are chromium-poor layers. At the same time, according to the analysis, C- was present on the surface of the rust layer at a concentration of up to 3.65%, and this C- did not disappear until the depth of the rust layer reached 100004°. Rust layer thickness in the range of about 50,000 °, the oxygen content is also up to 20% or more. It can be assumed that: due to the oxidation near the weld seam caused by the high temperature of the welding process, chromium is oxidized first and leads to the formation of a chromium-poor layer, and this welded part is placed in the ocean atmosphere containing a large amount of C moisture, and the chromium-poor layer rusts rapidly due to the action of C-, etc.

After the weld, after the removal of the chromium-poor layer by measures (sandblasting, pickling, etc.), the rusting problem did not occur again.