Hydrogen evolution on a steel surface and subsequent hydrogen diffusion into the steel matrix are evaluated using an electrochemical permeation test with no applied cathodic current on the hydrogen charging side. In particular, cyclic operation in the permeation test is also conducted to clarify the corrosion-induced hydrogen evolution behavior. In contrast to the conventional perception that the cathodic reduction reaction on the steel in neutral aqueous environments is an oxygen reduction reaction, this study demonstrates that atomic hydrogen may be generated on the steel surface by the corrosion reaction, even in a neutral environment. Although a much lower permeation current density and significant slower diffusion kinetics of hydrogen are observed compared to the results measured in acidic environments, they contribute to the increase in the embrittlement index. This study suggests that the research on hydrogen embrittlement in ultra-strong steels should be approached from the viewpoint of corrosion reactions on the steel surface and subsequent hydrogen evolution/diffusion behavior.

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

In this work, a nickel metal (Ni) electroplating on the activated carbon fiber (Ni/ACFs) surfaces was carried out to remove the toxic hydrogen chloride (HCl) gas. The surface properties of the treated ACFs were determined by using nitrogen adsorption isotherms at 77 K, SEM, and X-ray diffraction (XRD) measurements. HCl removal efficiency was confirmed by a gas-detecting tube technique. As a result, the nickel metal contents on the ACF surfaces were increased with increasing the plating time. And, it was found that the specific surface area or the micropore volume of the ACFs studied was slightly decreased as increasing the plating time. Whereas, it was revealed that the HCl removal efficiency containing nickel metal showed higher efficiency values than that of untreated ACFs. These results indicated that the presence of nickel metal on the ACF surfaces played an important role in improving the HCl removal over the Ni/ACFs, due to the catalytic reactions between nickel and chlorine.

The atmospheric pressure plasma treatments (Ar/O2 and Ar/N2) of activated carbon fibers (ACFs) were carried out to introduce hydrophilic functional groups on carbon surfaces in order to enhance the hydrogen chloride gas (HCl) adsorption. Surface properties of the ACFs were determined by XPS and SEM. N2/77 K adsorption isotherms were investigated by BET and D-R (Dubinin-Radushkevich) plot methods. The HCl removal efficiency was confirmed by HCl detecting tubes (range:1~40 or 40~1000 ppm). As experimental results, it was found that all plasma-treated ACFs showed the decrease in the pore volume, but the HCl removal efficiency showed higher level than that of the untreated ACFs. This result indicated that the plasma treatments led to the conformation of hydrophilic functional groups on the carbon surfaces, resulting in the increase of the interaction between the ACFs and HCl gas.

염화철(Ferrous Choloride) 증기의 고온 수소환원 반응을 통한 미립질 철분말의 생성속도에 대한 이론적인 해석돠 실험을 수행하였다. 철분말의 생성기구는 염화철이 증발하여 생성된 증기와 운반가스인 알곤을 혼합하여 반응부로 유입시키고 수소에 의한 고온환원반을을 통하여 철분말과 함께 부산물인 염화수소(HCI) 가스를 얻게 된다. 생성된 반응부 후미에 설치한 유기용매 포집기를 이용하여 회수하였으며, 염화수소는 가성소다 수용액에 흡수시키고 이를 적정함으로써 초기 반응물인 염화철의 전환율을 계산하였다. 반응속도식의 반응물에 대하여 1차반응(1st-order reaction)이고 염화철 증가와 운반체인 알곤가스가 평형상태일 때의 속도상수는 k=7,879exp(-53,840/RT)dm3/mole.sec으로 표시되며, 이때의 활성화에너지는 53.84kJ/mole이었다. 철분말의 TEM 사진에 의하면 입도범위는 0.1~1.0μm이며, 반응온도 및 가스유량에는 크게 영향을 받지 않는것으로 나타났다.

The purpose of the present study is to examine characteristics of hydrogen sulfide adsorption using iron-activated carbon composite adsorbents prepared by ferric nitrate and ferric chloride. Prepared adsorbents were discussed on H2S adsorption capacity. Also, adsorbents were analyzed by surface analysis methods for illustrating the physical characteristics of H2S adsorption. The breakthrough tests of H2S were conducted at 3,333 ppm of inlet concentration, demonstrating that the adsorption capacity for iron-activated carbon composite adsorbents was in order of FC_AC (Ferric chloride_Activated carbon), FN_AC (Ferric nitrate_Activated carbon), FC (Ferric chloride) and FN (Ferric nitrate). Adsorption capacity of FC was 0.06 g/g, whereas FC_AC showed the highest capacity of 0.171 g/g. All adsorbents exhibited the amorphous type in physical appearance based on XRD analysis and high Fe content based on EDS analysis. The surface areas of composites were increased by adding activated carbon, exhibiting better adsorption capacity.

In this study, the experiments which use the dry absorbent has been executed in order to find optimum HCl absorptionconditions. The absorbents in this experiment were Ca(OH)2-A, Ca(OH)2-B and CaO. They were put in a fixed-bed reactor.The reaction temperature of HCl/Ca(OH)2 systems were between 200~400oC and those of HCl/CaO systems werebetween at 500~700oC. The reaction gases were HCl and N2 mixtures (3000ppm). The reaction gas of 2L·min−1 wasfed into the reactor. As temperature increased, the conversion ratio of HCl in Ca(OH)2 particles also increased.Consequently, Ca(OH)2-B showed the maximum conversion ratio of 19% at 400oC. CaO also showed the similar tendencywith the result of Ca(OH)2. In case of same particle sizes, as reaction temperature increased, the reaction rate constant(k) also increased. The highest reaction rate constant of Ca(OH)2-B was 3,952min−1 at 400oC. All absorbents in thisexperiment showed that the reaction rate decreased with increasing the size of the particles at each temperature condition.The kinetics of the reaction between sorbents and HCl molecules showed that the activation energies were about 2.71~6.85kcal·mol−1 (averager 4.53kcal·mol−1) for Ca(OH)2-A, about 1.3011.51kcal·mol−1 (average 6.10kcal·mol−1) forCa(OH)2-B, and about 2.5314.3kcal·mol−1 (average 6.91kcal·mol−1) for CaO depending on conversion ratios.