Abstract
There are multiple references to sample cleaning methods prior to hydrogen content determination, or hydrogen spectroscopy analysis, but there is still no unified criteria; different authors use their own “know-how” to perform this task. The aim of this paper is to solve, or at least clarify, this issue. In this work, the most commonly used sample cleaning methods are compared. Then, five different methodologies are applied on certified hydrogen content calibration pins and on high strength steel concrete-prestressing strands and the three main situations regarding hydrogen content in the microstructural net (non-charged, charged, and charged and uncharged) are studied. It was concluded that the HCl solution C-3.5 cleaning method recommended by ASTM G1 introduces large amounts of hydrogen in the samples; but can be useful for eliminating superficial oxides if necessary. The rest of the methods had similar results; but the more complete ones that involve ultrasounds and last longer than 8 min are not appropriated when important diffusion may occur on the samples during their application. Simple methods that involve acetone or trichloroethylene and last around 1 min are preferable for almost all situations as these are faster, easier, and cheaper. As a final recommendation, as trichloroethylene is toxic, the simple acetone method is, in general, the most convenient one for regular hydrogen content analysis.
Highlights
Hydrogen is a very common element in the earth; it is present in both the atmosphere and the crust
An element that will coexist with materials in their structural applications. It is especially critical for high strength steels, because of the effects that hydrogen has on their mechanical properties. hydrogen presence in this type of steels mainly comes from two sources: the manufacturing process and from the environmental conditions that can take place in its structural applications
Calibration Pins and Wire Pins in As-Received State. Both the calibration pins and the wire pins were studied in their as-received state, in order to determine the initial hydrogen content; ergo the hydrogen introduced in its manufacturing process for wire pins, or the certified hydrogen content for calibration pins
Summary
Hydrogen is a very common element in the earth; it is present in both the atmosphere and the crust. The main forms in which it appears are in gaseous compounds or as part of water and geological compounds It is, an element that will coexist with materials in their structural applications. The behavior of steels in environments where hydrogen is present gives rise to embrittlement phenomena that depend on the material’s microstructure as well as on the hydrogen content in its atomic network. For this reason, it is of the utmost importance to determine the content of hydrogen trapped in the materials and its interaction with the microstructure. There are different types of samples to analyze hydrogen content, covered by the three types currently used by the manufacturers of hydrogen analysis equipment to calibrate their equipment; the melting pots and the ovens in the equipment are manufactured [12,13]: Pins: The most commonly used, generally of a mass of between 0.5 and 2 g and cylindrical shape (generally twice or three times longer than its diameter).
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