Evaluation of Hydrogen Degradation of Water-Wall Pipes by the Surface-Layer Properties of Magnetite

Abstract

We propose a simple procedure for the evaluation of the ability of magnetite to protect against the absorption of hydrogen based on measuring the degree of its adhesion to a metal and its permeability. The degree of adhesion was found as the fraction of the area of a part of the surface covered with a layer of magnetite relative to the total surface area of a sample cut out from a pipe and stretched by 20%. The permeability of the layer of magnetite was determined electrochemically according to the value of the stationary potential and the decrease in the corrosion current through the surface covered with magnetite as compared with pure steel. We determine the electrochemical parameters and adhesion of magnetite formed on the inner surfaces of various segments of the pipes of 15Mo3 and 10CrMo910 steels taken from two boilers and analyze the factors affecting the properties and structure of magnetite and, hence, the degree of hydrogenation of the pipes. The proposed method for the electrochemical evaluation of the quality of magnetite can be applied under field conditions for the estimation of the residual service life of the pipes and monitoring of the parameters of technological working media in the boilers affecting the quality of magnetite.