What type of corrosion is affecting this device made of 316 material?
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This post was last edited by julius6054 on 2019-9-29 09:50. Note: This device has been in use for 3 and a half years now. Two years after it started operating, leaks were detected at the bottom; internal dye penetrant testing revealed cracks, and welding repairs were carried out. However, as soon as the device was put back into use after the repairs, leaks occurred again at the same location. There are no leaks elsewhere on the device, and the surface of the 316 stainless steel material is in good condition. Equipment condition: 1. Made of 316 material; the equipment undergoes no heat treatment after processing ； 2. Medium: Cationic starch solution, at a temperature of 98°C or less, with a pH of 5.1.
This post was last edited by julius6054 on 2019-9-29 09:48
It turns out the photo is too large. . . . ;P
Is it intergranular corrosion? Over time, leakage points appear in areas where the weld quality is poor; essentially, the entire weld might be problematic, it’s just that the issues have not yet become apparent. Alternatively, a larger area around the leakage point could be rewelded – that’s just my personal opinion
Medium: Cationic starch; Corrosion: Pitting corrosion; Cause: Likely due to the presence of chloride ions in the raw materials.
Intergranular corrosion is suspected, as it only occurs at the cold bent area and the bottom of the container; there is no corrosion elsewhere. It’s a starch solution, but no analysis of the solution was provided.
The difficulty is why it appears only at the bottom and not elsewhere. Moreover, the leak points found were not at the welds either
The starch manufacturer says there are no chloride ions; of course, this sample hasn’t been sent for testing either
The starch manufacturer says there are no chloride ions; of course, this sample hasn’t been sent for testing either
After the equipment was manufactured, its surface was not properly treated@
The surface treatment meets the technical requirements specified in the drawings; the uneven areas seen are the result of weld repairs.