What causes 304 stainless steel bent pipes to turn black after acid washing?
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Recently, I was carrying out acid washing and passivation on a storage tank. After spraying the acid solution inside in a sealed environment for 24 hours, I noticed that the elbow section of the heating coil there had turned black, showing a clear difference from the surrounding area. Is it a quality issue with the pipe?
Sometimes such issues occur during pickling. 1. It is possible to check the actual composition of the pickling solution to see if its concentration is abnormal. 2. PMI can be used to examine the composition of the elbow