Hydrogen Entry Behavior into Iron and Steel under Atmospheric Corrosion

Abstract

Electrochemical hydrogen permeation tests of pure Fe sheets rusted by cyclic corrosion test (CCT) and atmospheric exposure were carried out under controlled temperature and humidity to investigate the influence of atmospheric corrosion on the hydrogen entry behavior. The hydrogen entry into the Fe specimens rusted by CCT increased under wet condition, and the hydrogen entry was increased with the CCT cycle number. During drying process after the wetting, hydrogen entry was further enhanced and a peak of hydrogen current was observed. The peak hydrogen permeation current tended to increase with the growth of rust layer, and the peak value of the hydrogen permeation current became remarkably higher than that at the highest humidity when the rust layer was relatively thick. Similar enhancement of hydrogen entry into an outdoor-exposed specimen was also observed during drying. Drying process after CCT resulted in an increase in hydrogen content of 5 mm-thick steel specimens measured by means of thermal desorption analysis, indicating the enhancement of hydrogen entry during drying process and showing a good agreement with the electrochemical hydrogen permeation test results. It is required to take into consideration the enhanced hydrogen entry to estimate concentration of hydrogen from the environment.

Evaluation of Hydrogen Absorption into Iron by Alternating Current Responses in an Electrochemical Hydrogen Permeation Cell

“…At this time, on the surface of the steels, hydrogen evolution reaction can be evolved as one of the cathodic reactions. According to the reports by some researchers, [1][2][3][4][5] in atmospheric corrosion, H atoms can be absorbed into steels during the corrosion in the atmospheric environments. For example, if the concentration of absorbed H atoms reaches in the order of sub ppm, 1 000 MPa-class steels may be susceptible to hydrogen embrittlement.…”

Electrochemical Hydrogen Permeation Test under Controlled Temperature and Humidity after Outdoor Exposure at Beijing, Chongqing and Okinawa

“…The exposure test was started in our previous study. 27) Although the 2-month-exposed specimen in our previous study showed discernible increase of hydrogen permeation current density under wet condition and under the following drying process, 27) the 2-year-exposed specimen showed no clear change in hydrogen permeation current density as shown in Fig. 6, except for a slight increase at the beginning of the drying process after the wet condition.…”

“…The current peak looks similar to the first peak of the specimen exposed at Chongqing for 6 months that appeared during drying process. In our previous study, 27) specimens exposed at Okinawa for 2 months showed slight Fig. 2.…”

“…The experimental set up was the same as that shown elsewhere. 24,27) The rusted specimen was fixed on a modified DevanathanStachurski cell, which was filled with a 1 M NaOH aqueous solution. A Hg/HgO reference electrode (E 0 = + 99 mV vs SHE (25°C)) and a Pt counter electrode were set in the cell.…”

“…[19][20][21][22][23][24][25][26][27] In our previous study, it was found using ECHPT during cyclic corrosion test (CCT) that the rust later formed during atmospheric corrosion has an important role on enhancing hydrogen entry. 25) ECHPT of Fe sheet specimen corroded by CCT 24,27) and outdoor exposure 27) under controlled temperature and humidity were also carried out for further understanding of hydrogen uptake behavior. The advantage of ECHPT under controlled temperature and humidity after outdoor exposure is that it is much easier than on-site ECHPT and that the exposure test can be carried out in any sites even in foreign countries where on-site ECHPT cannot be easily performed.…”