Abstract
A monitoring apparatus and some techniques to measure hydrogen content in line pipe steel over a long term have been developed and established, by using electrochemical permeation method (nickel-plating method).
This monitoring system consists of cells for nickel-plating and monitoring, which are made from acrylic resin, pumping equipment for supply of electrolyte and electronic equipment (YOSHIZAWA type). The cells can be easily set at any position on the external surface of the line pipe. After nickel-plating, the monitoring cell is set and filled with 1N NaOH solution and then the electronic equipment is operated potentiostatically at 150 mV vs Hg/HgO. Anodic current decreases gradually to the value less than 0.04 μA/cm2 within one day. After such preparation, the hydrogen content can be monitored. The detection limit of the hydrogen content by this monitoring system is 0.01 ppm.
The field test for monitoring hydrogen content in line pipe is performed with high reliability over three months.
