In one of our CDU’s recently we had a leak on the joint between the ¾” overhead neutralizer injection line and 24” overhead vapor line of atmos column. Internal corrosion was observed on the leak area. The pipes thickness was measured at different parts around the leak area and found to be OK. It indicates localized corrosion. We are using neutralizing amine as neutralizer. We are unable to find the root cause of the failure. Are there any instances like this in other refineries? If so, what might be the probable reasons?