Why does the water distributor with a 316L frame corrode in resin columns lined with PO and in composite 316L resin columns...

Thread Content

This post was last edited by zz7608210714 on 2020-9-5 17:51. Hello, experts! Recently, I encountered a typical case of Cl- corrosion. One interesting phenomenon in this regard is that for water distributors with the same material, structure, and manufacturing process, when used in columns lined with PO resin made of low-alloy steel or columns made of low-alloy steel combined with 316L resin, the corrosion that occurs under identical operating conditions and medium environments differs significantly. I would appreciate it if some expert could explain the reason for this. Details are as follows: 1. The equipment used on-site can be divided into two types: carbon steel columns lined with PO resin and 316L composite steel plate resin columns ； 2. Material of the resin column water distributor main pipe and the fishbone-type water distributor frame: 316L; connection between the two: threaded connection ； 3. Mild crevice corrosion occurred at the threaded connection between the 316L composite steel plate resin column fishbone-type water distributor and the main water distributor pipe ； The local surface at the weld area is rust-colored, while the vast majority of the surface is shiny silver ； 4. Severe crevice corrosion occurred at the threaded connection between the carbon steel PO resin-lined column and the fishbone-type water distributor ； Severe pitting corrosion on the welds of the water distributor, and severe corrosion on the welds of the main pipe. Question: Why is the corrosion of the welds on the main water distribution pipe of the carbon steel-lined PO resin column, as well as the welds on the water distributors and the connection threads, much more severe than the corrosion in corresponding areas of the 316L composite steel plate resin column?