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In this study, hydrogen absorption behavior of steels on a vehicle during driving and parking in deicing-salt-spraying areas was investigated by using temperature-compensating hydrogen absorption monitoring system. During the driving of the vehicle in the areas, hydrogen permeation current of steel was increased due to picking up of salt water from the road when the road was wet. On the other hand, during the parking of the vehicle, the magnitude of the hydrogen permeation current were indicated that the hydrogen permeation current in the automobile driving environments is related to both driving states of a vehicle and environmental conditions such as temperature and relative humidity.

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Effect of temperature and chloride deposition on hydrogen absorption into steel was evaluated under wetdry cyclic corrosion conditions by using a temperature compensated hydrogen absorption monitoring system which is based on electrochemical hydrogen permeation method. Peaks of hydrogen permeation current were detected during the wetting and drying periods in the wet-dry cyclic corrosion conditions. Hydrogen absorption was increased with increasing temperature and chloride deposition. It was suggested that the hydrogen absorption behavior under the wet-dry cyclic corrosion conditions is related to the change in solution chemistry during the wetting and drying periods where the increase of chloride ion concentration and the decrease in pH due to hydrolysis reaction of Fe 3+ occurred. Based on these results, the amount of absorbed hydrogen map effected by temperature and chloride deposition in atmospheric corrosion environment was described.

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To develop high strength steel with high resistance to hydrogen embrittlement, it is necessary to clarify the mechanism of hydrogen entry into steel. Hydrogen entry is caused by corrosion reaction under atmospheric environment. However, the relationship between hydrogen entry and corrosion behavior, and the influence of environmental factors on the hydrogen entry such as temperature, relative humidity (RH) and salt deposition are not fully understood. In this study, simultaneous monitoring of both hydrogen entr y and corrosion rate was employed to investigate the influence of environmental factors on hydrogen entry and corrosion behavior. The monitoring was conducted under the atmospheric exposure test. As a result, hydrogen entry and corrosion rate increased with increase of amount of salt deposition. Corrosion rate increased with increase of RH, whereas hydrogen entry had a maximum at medium RH. The mechanism of promotion of the hydrogen entry at medium RH range was assumed to be related to lowering pH due to hydrolysis of Fe 3＋ in high ［Cl − ］ environment.

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