Behavioral Analysis of Hydrogen in Metals under the Effect of H2S Corrosion Using a Layer-stripping Micro-hardness Technique

In order to study the distribution behavior of hydrogen in metals under the condition of H2S corrosion, a layer-stripping micro-hardness test was designed to analyze the hydrogen distribution along the depth of hydrogen-charged 45 high-quality structural carbon steel at three different hydrogen sulfide concentrations and four corrosion periods in this study. The results show that there is a terminal solid solubility of hydrogen in the metal for hydrogen sulfide solutions over various concentrations and corrosion periods. A hydrogen-saturated layer is produced by hydrogen diffusing through the metal from an unsaturated state to a fully saturated state. The hydrogen-saturated layer is not affected by the concentration of the corrosion, but its thickness increases as the corrosion period increases. In this way, we established a new hydrogen diffusion model in metals.

Protection of materials from hydrogen accumulation

The article is concerned with possible accidents caused by high concentrations of hydrogen in metals. The problem of using recycled metal is considered. The mechanisms of hydrogen accumulation are described. Among other things, we propose an introduction to the output control of hydrogen concentrations. The results of reducing the concentration of diffuse-mobile hydrogen in steels after ultrasonic treatment are described.

Effects of anisotropy and regime of diffusion on the measurement of lattice diffusion coefficient of hydrogen in metals

The lattice diffusion coefficient of hydrogen in metals is commonly measured by permeation tests. Such tests assume isotropic diffusivity with a set-up which measures permeation flux only along one direction. The measured values of the lattice diffusion coefficient are strongly influenced by the trapping of hydrogen at microstructural defects. These factors lead to highly inaccurate determination of the lattice diffusion coefficient, more so in an anisotropic medium. In this work, we present a three-dimensional (3D) diffusion equation in non-dimensional form for an anisotropic medium with source and sink terms which account for detrapping and trapping of hydrogen. The concentration of hydrogen at lattice and trap sites is assumed to be in a local equilibrium. An initial boundary value problem of the permeation test is formulated and the governing partial differential equation is implemented in a 3D finite-element code. The influence of anisotropic diffusivity on the measurement of lattice diffusion coefficient is shown by numerical simulations. Asymptotic analysis of the governing equation reveals that the lattice diffusion coefficient can only be measured in certain regimes when performing permeation tests at varying temperatures. The nonlinear behaviour of Arrhenius plots of diffusion coefficient versus inverse of temperature due to trapping is analytically and numerically predicted.